I have to ask:  Are you suggesting that the afterlife Is merely a place for preparation for return to earth?  

The problem with that may be what is nervana or the ultimate destination?
Another might be in the suggesting the earth as the only place to learn and grow.

The spirit world is vast beyond our comprehension, I am definitely not suggesting that it is a place just for the purposes of returning to Earth. Earth is one of many schools or playgrounds of learning albeit a more difficult one as it is both a mental and a physical world, there are other worlds in which souls learn and progress which can be just mental or just physical. You will find a more detailed response to your questions if you read Michael Newton's 2 books; Journey of Souls and Destiny of Souls

gotta be an interesting read. You refer to it a lot. Who's the author?

It's confusing for these people with no specific psychic abilities (like myself) or no tangible connection to the other world, because we are left with only what others write on the subject to work on.

In all rationality though, this "model" that you speak of, of learning schools and experience... well, something doesn't feel right when reading about it, like it's an incomplete explanation that leaves too many questions unanswered.

I believe the one I raise is a valid one, yet most of what you read on the subject or get when asking this question is the same as what you said. "can a spirit disappear?" "no it can't. You are on a path to development". "do you have to be on this path?" "yes" "why?" "cause it's the rule" "why" "just cause" is pretty much what one gets :D

The author is Michael Newton, who is a clinical hypnotherapist and his books are based on thousands of case studies and research. We all seek the truth and all knowledge, however, if we are not ready in our development then that knowledge will not be revealed to us until we are ready. Only the all knowing (God) has the complete explanation and even if a soul in a human body was given all the information and the full explanation, it would not be able to comprehend it or be ready to receive it.

Choice is the key in our existence, you don't have to participate in your development as a soul, but the motivating factor of your existing progress becoming stagnant is the driving force to continue in your learning & development. There is no rule but there are paths and choices to be made and one makes those choices based on what one holds dear and a clear goal in mind, the thirst for knowledge being one such goal.