My husband's second affair occurred about 8 years after the first. He was military and in both cases he was away from home.
I will explain the differences between how we handled the first affair and the second because I'm assuming you want some reassurance that everything has been done that can be done to prevent a recurrence.
After the first affair, I accepted the blame. He did very little work on himself. Yes, he appeared genuinely sorry and I mistook that for remorse. In hindsight, I believe now that he was regretful rather than remorseful. Because I accepted the blame and internalized his reasons, I worked on myself. Society often blames the BS for not being good enough in some way and I bought into that. I tried to become all the things I thought a wife should be because, after all, if I was a better wife he wouldn't need to cheat. So, while I was addressing all of his complaints, he was essentially getting away with it. Sure, I was devastated and he felt bad about that but he also reaped huge rewards for his behavior with no real consequences. Unfortunately, the first affair was in 2002 and I hadn't found SI yet.
By the time I did find this site I figured out I had actually done only one thing right. In the beginning, when he was back and forth on the fence, I pushed him off the fence. I told him I was moving on as if he wasn't coming home because it wasn't fair to me be in limbo while he screwed around in another country trying to decide if the single life or some floozy with low standards was what he wanted. Other than that, nothing else was done and by 2005, when I found this place, we were so far along and, I believed, fully healed and reconciled. I never went back and requested any of the work. So, he never tried to figure out why his response to his "complaints" about me was to cheat. He never looked at the factors that helped him get to the moment where it was okay in his mind. He never looked at what boundaries he crossed that led up to cheating. He never asked himself why lying and conflict avoidance was easier than facing and working through a problem.
After the second affair, I wasn't having any of what happened the first time. I accepted not one iota of blame. I would say I made him do his work but I didn't make him do anything. I gave him a choice: Do the work or lose the marriage. I was fully prepared to walk away and he knew it. I didn't fall apart this time. I wasn't even shocked this time. After all, it wasn't like the first time when I thought my husband wasn't capable of betraying me.
If you are worried about a recurrence this is my advice:
1. Make sure your WS does the work and doesn't just give lip service to doing the work. Actions should match words. Good boundaries should be there whether you are there or not. Transparency should be volunteered, not forced. Responses to stress should be healthy discussion, not conflict avoidance and lying. Remind your spouse that he has a choice: He can do what you need to feel safe remaining married to him or he can not be married to you. Then let him make his choice. His actions will back up his words if he wants the marriage.
2. You worrying about your spouse cheating won't stop your spouse from cheating. Worry will, however, cause you health issues. Don't waste your time and energy on worry. Worry when you know you have a reason to worry. If everything has been done that should be done to prevent a recurrence, at some point, you have to let go of trying to control it.
3. Past behavior of your spouse is a pretty strong indicator of whether he or she is reconciliation material (in my opinion). Has he consistently taken responsibility for his actions in other areas of his life? When he screws up at work does he own it or is it someone else's fault or does someone always have it in for him? Does he have a history of his family making excuses for him? Does he have a history of allowing people he cares about to make excuses for their bad behavior? The reason you want to examine this is because if your spouse already has a history of making excuses instead of taking responsibility and doing the work to fix his issues, it's unlikely that he will take the initiative now. Someone who always has a bunch of excuses is very good at continuing to find excuses and not so good at holding himself accountable. But if he's always taken responsibility without excuses in other areas, this one is not likely to be any different once he sees the importance of it.
As far as square one goes- I was never back at square one. Thanks to all my reading here, I was way ahead of the game after the second affair. The advantage you have is that you have this resource now at the beginning of your reconciliation. That's not a guarantee but there are no guarantees with relationships no matter who they are with. You can take a chance on this one or take a chance on a new one down the road. That's up to you.