My opinion is that there is always a very good chance of at least an EA. I think the guilt factor is entirely over-rated as an excuse why they won't come back, etc. In my experience and reading here, most WAWs (I'm not sure that's true of cheating husbands because they like to have the opportunity to have the chance to return without being found out), if the affair is discovered, it's still your fault and they aren't remorseful, nor does she feel guilty. First of all, because it's your fault she looked elsewhere and secondly, "she didn't feel married anymore anyway". Actually, if you do find out I think she'd be more likely to either say it occurred after separation (when they don't consider it cheating) or say that it doesn't matter anyway because they already want out of the marriage.
It doesn't matter whether it's out in the open or not because you won't rebuild a marriage until she wants to rebuild it. There is no sense even worrying about that until she asks to try again. It would be to your favor if she's having an affair because when it's over she'll be more inclined to come back than if she simply left because she doesn't want to be married to you.
In the end, it's not the years in your life that count. It's the life in your years. Abraham Lincoln
It is hard to fail, but it is worse never to have tried to succeed. Theodore Roosevelt
