From ILYBINILWY back to ILWY ... possible?

Yes, it is possible. The hard part is this: Upon DDay the BS is ILWY, they ideally need to take steps to end the affair, AND be strong, loving, and caring at the same time. The WS might then come out of the fog, realize how idiotic infidelity is, and how they rewrote history to demonize the BS, who isn't bad after all, actually they are pretty good, though they're human, and have their faults. The WS realizes the BS actually is ILWY, and that's pretty amazing, considering, so the WS gets back to ILWY. BUT the withdrawal takes time, the fog dissipates slowly, the WS might have some relapses or slip ups along the way. The BS has tome to mull things over a bit maybe, anger and self respect come into play. Now things are really tricky, because you get 2 moving targets that have a narrow window to line up. The WS's feelings and actions need to rebound high enough, fast enough to hit the BS's feelings before they plummet to the point that the BS will withdraw irretrievably. I went through this, and I think it was close. Very close. Her goodwill skyrocketed as mine was faltering.

Still, if the 2 are stubborn enough, they can survive the targets missing, and persist long enough for other reasons, until goodwill returns on both sides. I'd say wazza did this.

SadandAngry's answer is pretty good. I'm kind of an odd ball in this situation because I was never not in love with my wife. Before everyone throws tomatoes at me let me explain a little. First - I'm over two years post Dday and fortunately my wife and are very successfully reconciling. What I say I know to be true after years of introspection, self examination, and countless conversations with my wife. When my EA started I believed I was very happily married - I believed the state of our marriage was what a happy marriage was supposed to be. The truth of the matter is that through the years and two kids my wife and I had slowly taken each other and our marriage fore granted - but neither of us realized it. So in a strange and ironic twist of fate my EA actually reawakened feelings and needs in me that I had forgotten - feelings and needs that were laying dormant for my wife. While my EA was ongoing I couldn't help but express those reawakened feeling for her - I was growing to be more ILWH and at the same time I was neck deep in an EA. I swear the dichotomy of it all almost made my head explode. So in the days shortly after D day my wife and I reconnected and very fortunately experienced hysterical bonding. Like I said - my story is kind of an odd ball.

I think getting back to ILWY is so dependent on the individual circumstance that it's hard to characterize. No doubt it can happen, it can also not happen, it can happen to late, it can appear to happen and be a lie. It's just very hard to predict. I think the only way to have any clue is to watch the cheater. Genuine remorse isn't hard to recognize when you see it. Someone who is really remorseful and is really doing the work of reconciliation is very likely either back to ILWY or getting very close to it. Only love would give someone the strength to really do the heavy lifting. Just my $.02