I am 8 years older than my H, even though I don't look it. It had never been a problem until MLC hit. I know a lot of MLCers are obsessed with youth and fears of growing old. May be it could be a trigger when they are trying to stay young. My Hs OW is the same age as him, but he has in fact gone for a younger woman, when comparing her to me.
This had actually crossed my mind a lot, very interesting.