Its also possible that it started long before he showed any signs. Think back - did he show any signs of discontent or start questioning his life even before he identified his change of feelings?
Or another possibility, as Exquisite says, is it may just be a transition that almost became a crisis. I believe there is a spectrum, not a boundary, between transistions and MLC. That is why we see different types of MLC -some long, some short, some mild, some almost violent in nature. I read that it is the catastrophic effects on the person and the family around him/her that makes a transition into a crisis.
Hopefully his questions, his confusion will be resolved by his insight and make his transisition quick. If so, you are one of the lucky ones.
That is why you rarely hear of a single person having an MLC - its because there are less people affected by whatever they are going through.
I kind of sense that for my h, this was a brief transitional thing, but I think he will have much more to work through for a long time. He's in a good place now, and our conversations are way more honest than ever. I really like that. He tells me that if he spends more time doing what he used to love, and if we work on our intimacy, that he's going to feel good again. We'll see. We are planning to go to retrouvaille in February after the move is settled. I read your thread and it was encouraging to me.