I recommend coming down HARD AND FAST when there is a definite PA or EA, the betrayed spouse knows, the wayward spouse KNOWS that you know, and then they are unrepentant/in-your-face about it. Because in those situations, a lot of damage can be done by the entitlement-fueled wayward spouse, and they will also rapidly lose respect (and therefore attraction, and therefore LOVE) when they perceive the betrayed spouse's "standing" as a sign of WEAKNESS.
I agree with that Starsky. I would also say that there are some Waywards who lie and hide the fact they are interested in someone else and/or are having an affair. They keep the BS hanging for months on end. Many will NEVER admit it until finally getting caught and even then, some will keep denying while the BS keeps giving them the benefit of the doubt.. Time after time after time.
I find many BS's almost helping the WS hide the affair because what they don't know doesn't hurt them and also if they don't know, they come to the conclusion that means there is no affair. I think it is hiding one's head in the sand. They take the no snooping to the opposite extreme. They refuse to even consider any evidence..............
So whether they know for sure there is an affair or whether they don't know for sure there is an affair, doesn't mean there isn't one going on. Affairs thrive on secrecy. Some allow it to go on because of the fear of knowing the truth and maybe aren't ready to handle it. I can't tell you (and I am sure you know too, Starsky) how many people on this site alone that I have heard say their spouse is not having an affair, only to learn later (and sometimes months and months later) that they were indeed wrong. They are then thrown back to square one emotionally and feel like they have to start all over with the whole process, which could have been avoided by finding out what you are up against right from the start instead of taking all the blame the WS throws at you for months on end only to realize some of it is a smokescreen for them having an affair by throwing the guilt on the BS and their supposed failures.