I'd say, the many facets of '
physical' existence in these cases, as there are countless ways, and the soul is managing more life at once, even beyond the physical, paralell to each other.
I also believe that the soul has nothing to do with 'moral purification', as moral itself is something 'humans' put into shape and word, and karma, for example just the consequences of an action; it doesn't try to teach you moral, it's more about responsibility, and what may happen if you live without taking it.
A soul may want eperiencing, learning and expanding itself, and in some cases, it is obvious that the 'task' a soul have to deliver is beyond just simple individual achivement, and has a wider range, with a
group of souls involved, in co-operation for a greater matter. Sometimes, some of the participants are not even reincarnated, just one or a couple, while the connection is active. I've experienvced it in myself. Take it as landing on an abandoned island a group want to explore, and for strategic matters, one side of the group stay on the air, in their laboratories, helping and operating behind, while the other(s) are on the Isle physically, and doing their part.
Although, naturally, returning souls in one's life is common, and 'families of spirits' tend to navigate through lives together; not necessarily sticking together all the time, but often, swapping roles, the nature of connection, even. The one you married in a previous life can be your greatest enemy in the next, yet the soul carries no grudge, these are roles, and experiences the souls deliver.
I think, a soul can reincarnate any moment if there's a goal having to achieve, it doesn't even mean they'll 'stuck' in the reincarnation cycle if they
'fail to draw moral conclusions and live by it'. It can chose not to born in the next couple of hundreds years, or not at all, or it can chose to start the new one once it's went through the process, and found a new location, family, circumstances to pick and born into.
ㅤBecause yes, they can go as far as chosing this one and they can even re-arrange their decision, in the form of the child dying before it could even take it's first breath outside of the womb. It happens.
Truth is, many deaths are not accidental, and has nothing to do with unlucky outcome. If someone has to go, they has to go. Then they'll go the most unluckiest or even 'silliest' ways, and the ones who have to live, will survive a lot of unlikely things until they carried out what they need to. It proved me right so far, because I myself should not be alive, and it happened multiple times, going against the laws of the physical world.
what happens to a very old soul that has already experienced most of what life can offer
I think, that a soul won't turn into a 'very old soul' even if they went through thousands of reincarnations. Why? Because a soul's age often reaches beyond human existence, or the Earth's existence itself, therefore, you can see very old souls reincarnate first, even, but also, very young souls having over hundreds or thousands of incarnation, and yes, sometimes, you can still tell which soul is older, despite lived less lives than the younger one - but the opposite can also happen.
So I'd say, the age of a soul does not define which stage it is in the reincarnation cycle and when it can leave it.
I believe once the soul
knows or judges that there's nothing to gain from a reincarnation in the given moment (or no one to co-operate with for a 'greater' or collective matter), it won't turn energy into doing so, and focus on other aspects, although, again, they do run multiple lives at once, because we have paralel lives on many level, and it is actually can influence each other, even, or informations seep through from one to an another.
My approach may not be popular neither true, but through my experiences, these are my conclusions on soul's existence on the material plane and I'm at peace with it, but of course, always open to hear out others, and experience more, to perhaps complete the puzzle, or re-arrange if I feel like it should be.
@Aldebaran Whether moral purification or completeness of experience... How can we achieve either if there's a memory wipe?
Memory wipe is for the physical body. The soul already possess the knowledge and experience it needed, and it proceed.
Usually, it manifests as lessons/wisdom/knowledge they don't need to explose in the next life for decades, because it comes to them far quicker, so they won't spend a lifetime trying to chase it until they finally learn.
Be it a knowledge, wisdom, a view, or even skill. Have you seen kids having talent in some things adults fight for over 10-15 years to achieve? It happens quite often. Souls can carry knowledge, and if they feel like they walked the path to embrace and live it, in the next life, it won't be a struggle to gain that knowledge. Either growing up in an environment where this wisdom is given, or having a personality that, this time, draws the conclusion quicker than a lifetime.
Me and my mother is a good example of this. The conclusions that I draw as a 9 years old kid, it took her 50 years, and now she lives better. It's common.
Have you seen people drawing significant conclusions from their life on their death bed? Same thing. They won't struggle with it in the next, and have it wasted or missed.
This cycle is often (not always) reason why some people are already far ahead of others from young age too. They simply have a greater progression and they don't need to struggle with it in the next.