In my case, the answer was "Yes". A few months after my divorce, an old ex-girlfriend from my school days knocked on my door out of the blue. She was married at the time. She instigated a kiss, one thing lead to another, next thing you know, we were in the bedroom. She showed up one more time after that, then I pretty much lost contact with her. This was a little over 20 years ago. Most likely my own fault, because I drunk dialed her a few times, not really aware of what I was doing.
If I had still been married, I wouldn't have done that (I personally wouldn't cheat if I were in a relationship), but being divorced, and she was offering, I figured, "Why not?". That was something we never got around to when we dated back in the day.
Would I do it again if "Barbara" knocked on my door? You bet your sweet bippy I would. I tend to think back on that event on a fairly regular basis... probably because that was the last time I've had sex.