I agree, specific circumstances must be considered. I just happen to think the "fizzling" of affairs is not quite as common as people would like to think.
That is not to say the R (the affair) is good after the initial lust/fun/newness wears off but as many of us have come to understand people stay in R's for a long time even if they are not "good".
There was not any abuse in my marriage. In fact, for the 10 years we were married my H played the role of doting and "super husband" like it was his job. When I began the diagnosing process for my SLE he started silently resenting me for being sick. On the outside he seemed like the perfect husband supporting his sick W... going to all dr's appts and so on but inside he started resenting me. Within 2 weeks time my dad died, I was officially diagnosed 6 days after my dad died and a week later my mother-in-law was also diagnosed with a rare genetic disease and my H shut down (internally).
We have talked about this post separation. He simply could not handle it and chose not to verbalize how he was feeling or reach out. My H does not like to be alone and he told me he needed to be with somebody that was not sick as that is what he wanted... a non-sick wife/partner.
My H will crash and burn again but I would be STUNNED if he left the R he is in. The R is now past the fun/lust stage and is getting real but he told me he will stick it out. My H feels happiness is achieved via external forces (EX: a R) and not something he should be responsible for on his own.
There was all kinds of dysfunction in our marriage. I just wasn't aware of any of it.
And FTR, once I was diagnosed I asked him to go to a support group with me for spouses and he said no. He also declined the offer to meet w/my health crises C. He started reading ONE book my dr. suggested and he never even bothered to finish it.
It wasn't that he was wrong to feel how he felt but it was terribly, terribly cruel to hide it until he snapped then deal with it by cheating.
My H's GF is very controlling, he says things aren't great but he is trying to stick it out. He is not allowed to talk to me at all. My H lost just about all his assets in our legal proceedings and he was okay with that as his GF just wanted our case done. Very sad (but worked out ok for me, lol!).
When spouses don't deal w/dysfunction it is a recipe for disaster. The only thing worse is when one spouse HIDES their real feelings and acts the part so the other spouse has no clue. My H wasn't looking to solve anything as he still says to this day it is all my fault. He was just looking for his normal. I think many people are looking for just that... their version of what life *should* be. The problem is they turn to another when all they need to do is take a look at themselves.