Well, most of this is just a guessing game, right? Nobody can see what's going on in their heads except the MLCer themselves, and even if they come back they are often closed up about the time they were gone.
My best guess is the shame and guilt is from day one. Heck, my MLCer wrote to me just a few weeks later admitting his feelings of guilt. Remember, guilt is selfish, it's about them and how they feel, not at all about how we feel.
I do have some interactions with my vanisher and I still see the shame and guilt even though I have mostly been kind and/or bit my tongue many many times.
Lately our interactions have dwindled again,... Why? Well, he's getting married, I think maybe even today, so his guilt and shame is increasing, time to avoid Nah again. Oh, he will be back once the wedding is done.
As for the replay being longer or shorter.... timelines again is all about them. From what I see on this forum over the years, the quick returners are very often not done, so let the vanishers do what they need to do, we are better off with them cooking far away from us.