Eremitical solitude is not transitional, nor is it escapist or individualistic. One may need a period of transitional solitude when one leaves a given context or situation (like active ministry or religious life) just as one will need some times of transitional solitude during bereavement, for instance, but whether these will ever grow into eremitical solitude is unlikely or at least uncertain given the rarity of eremitical life itself. One needs to take care with the type of solitude one is dealing with in a candidate and since types or forms can and do overlap and confuse, it can take time to determine what one is dealing with --- more than it takes in community, for example.
A Process NOT a Program:
These will be reflected by the Rule she writes for herself at any given stage of discernment and formation, and the Rule will serve as a guide for discussions re the presence of an eremitical vocation, readiness for profession, resources required (extended time in monastic silence, lessons in praying the Divine Office or other forms of prayer, assistance with establishing cottage industries, classes in theology, Scripture, instruction in the vows, etc). There should be a clear difference in the first Rule a would-be-hermit writes and the second, or third, or seventh, or tenth!! The formation team should be able to see progress in the person's lived experience and understanding of canon 603 and its constitutive elements. More, they should see signs that the person is growing in personal wholeness and holiness, that she is thriving in (and toward!) the silence of solitude even in the midst of the struggles it will also bring or involve.
In such a process the canonical stages appropriate to cenobitic life (life in community) simply have less meaning and are less quantifiable or even distinguishable. In any case such "stages" would need to be applied not according to a specific timetable, but according to one's readiness for the responsibilities associated with each stage of the life per se --- and these are not the same as those in coenobitical life. (A hermit is not being prepared to take on varying degrees of canonical responsibility within a congregation, but instead is being prepared to take a representative place in a living eremitical tradition.) It seems to me that the marker of such readiness is the capacity to write a liveable Rule of life after having written several experimental and less adequate Rules reflecting the would-be-hermit's growth in the life.
On mistaking the inability to write a liveable Rule as a sign of no vocation:
I have known people desiring to be c 603 hermits who spent several years trying and failing to put together a Rule. This did NOT necessarily mean they were not called to the life, but rather that they had a good deal to learn and especially, a lot to become consciously aware of before they could articulate it in the way a liveable Rule requires. For instance, to write a liveable Rule which concretely reflects a commitment to be open and responsive to God at work in one's life, one needs to cultivate all of those skills which are part and parcel of truly listening to/for God. One needs to know something of Who God is and who they themselves are, how God has been at work in their lives and the ways they have responded most fruitfully or refused to do so and why. Until one reaches some real degree of this level of awareness, they may be a lone individual, but they have not entered into eremitical solitude --- even as a novice hermit --- and they are certainly not ready to write a liveable Rule of Life.This means the first several years of beginning to live as a hermit may be full of learning entirely new things, developing new skills, becoming aware in ways one was not aware before, and essentially undergoing a unique kind of conversion of mind and heart which is necessary to being a hermit in some "essential way". The process cannot be rushed, nor should it be shoehorned into the canonical time frame that works for religious living in community. And yet, this shoehorn approach is the one most canonists take, and so too, most dioceses that decide to implement c 603. If a person has not written a liveable Rule in the first couple of years after approaching a diocese with a petition for profession under c 603, dioceses are apt to dismiss them as unsuitable candidates for such a profession.
Partly, I believe this occurs because the diocesan personnel don't have the first clue about how to accompany a budding solitary hermit on their own journey of discernment and formation, and partly it is due to the more fundamental failure to understand the distinction between lone individual and hermit in the first place. Equally foundationally problematical is the fact that diocesan staff, never having tried to do this themselves, often seem to believe writing a liveable Rule is a simple task that anyone should be able to do without assistance or significant preparation. Nothing could be further from the truth. Sometimes candidates are dismissed as unsuitable because the diocese doesn't actually believe in the hermit vocation at all --- though this lack of belief is rarely explicitly admitted; in such instances dioceses will not be able to accompany a candidate in the way needed. After all, if one does not esteem the vocation, one will hardly take the time needed to appropriately regard the process it requires for a candidate to embrace and be able to represent such a vocation! The process I have outlined on this blog serves to assist both the candidate and the diocese in taking solitary eremitical vocations seriously in a way which is organic to the vocation, to canon 603 itself, and therefore, is not unnecessarily onerous to either the candidate or the diocese.
Necessary Time Limits:
Your question about what is equivalent to the "perpetual doctoral student" problem where someone keeps writing and writing on their dissertation but never concludes it is well taken. There must be some time limits --- or at least there must be signs the hermit candidate is moving towards perpetual profession and the wholeness/holiness of an authentic vocation --- if the formation team is to continue working with them effectively. Otherwise, the process breaks down and everyone's time and energy are wasted. On the other end of the scale, there must be minimum time limits as well. A diocese must be clear that formation in religious life, while helpful, is not identical to that of the solitary hermit, nor in the Roman Catholic Church is canon 603 meant to define a "solitary religious" as the Episcopal Church allows in their canon law, but rather a true and solitary hermit (who is also, therefore, a religious).
For someone leaving religious life in community (especially in active ministry), time for transition from life in community and active ministry, to adult life in a parish environment (presuming they entered relatively soon after college), to contemplative life (if one really feels called to this), then to contemplative life in solitude (again, if one continues to feel called to this), and then to eremitical life per se must be given and required. This is so because each of these steps (especially in the beginning) can take various vocational forms, and these too must be discerned and established. Again, asking the candidate to write a Rule of Life which reflects her growing (or shifting) sense of these realities in her life can serve as a focus for ongoing discussion, direction, formation, and discernment of readiness to move in a somewhat more formal way from step to step toward profession as a canon 603 hermit. Time frames can serve as guidelines in all of this and for a lot of it, one needs only a good spiritual director.
It is only once one is transitioning from contemplative life to even greater solitude that one begins discerning eremitical life per se and may reasonably consider and discern consecrated eremitical life under c 603. At this point approaching a diocese is meaningful, but not truly before this. When one approaches a diocese prematurely (especially before one is a hermit in the essential sense I mentioned above) one may merely ensure that one's true vocation is not realized, much less recognized.
On the Problem of Shoehorning "Vocations" into more usual Canonical Timeframes:
While there are a number of benefits to the process I have outlined, one of its real strengths is the fact that it does not ask a person to approach a diocese prematurely but allows a person to work carefully with her director until it is relatively clear that she really has an eremitical calling. At that point the person has already undertaken a significant personal discernment process which she can then share with the diocese and should be relatively ready to discern with her diocese whether or not she is ultimately called to a canon 603 (a solitary diocesan hermit) vocation. If a person approaches the diocese before this (before, that is, the various transitional forms of solitude, etc., have been worked through, for instance), everyone involved may mistake being a lone pious individual, for being a person with a vocation to eremitical solitude. Professing a lone individual who then calls herself a hermit is destructive to the vocation per se and will make canon 603 itself apparently incredible. On the other hand, if one approaches a diocese prematurely, a diocese can err in the opposite direction, and may decide the process is taking too long and simply dismiss the person as unsuitable for c 603 profession.The tendency to shoehorn c 603 vocations into the canonical time frames associated with canonical religious life in community makes either of these mistakes likely. In the first instance, the eremitical vocation is demeaned or trivialized, and the diocese may decide not to risk professing anyone under c 603 in the future. In the latter instance, a specific public (canonical) eremitical vocation which is a unique gift of the Holy Spirit, may be lost to the Church even though the individual can continue to live fruitfully as a privately dedicated (non-canonical) hermit. Remember that canon 603 was originally written because a number of vocations to eremitism with long preparation in monastic life had no way to be recognized canonically or lived according to the monastic house's proper law.
As a result, years lived in solemn vows had to be relinquished, the monastics secularized, and ways to live as hermits explored apart from publicly vowed religious life. The long preparation for such a call was not accidental to discovering a vocation to eremitical solitude, but essential to it. For this reason, canon 603 also requires long preparation even though the diocese is not directly involved in most of it. This cannot and must not be forgotten; it is part of the canon's own history and nature.