Perhaps... a theory, if you will... the transitions become a crises... perhaps in part... perhaps in LARGE part... that the person in transition begins to feel smothered by the LBS, when all the WAS wants... is space.
I think this is pretty accurate. The challenge is, the crisis usually carries with it things that are destructive to the marriage (infidelity, squandering of marital assets, even poor parenting). How to effectively allow the time and space for such a "transition," without allowing/enabling the destructive behavior that often accompanies it?