Also, plainpain, I just read your post in general.
My FWH was 36 during the A. OW was 20. A YOUNG 20. The wide eyed, giggley, "you're the best ever, Mr. help, you're so COOL!" 20 year old.
I was 24 during FWH's A. My co-workers have always joked that I was "2_ (whatever age) going on 50", because I'm serious and hard-nosed, and OW was an overgrown 14 year old.
When she saw FWH, she saw the greatest man who ever walked.
When I looked at FWH, I saw FWH. And at the time of the A, my opinion of FWH wasn't all that high.
Honestly, I believe this is the root of most of the As I have known of. FWH got the ego boost because some ditzy, idiot 20 year old was over-the-moon about him, told him how under appreciated he was, how awful I was, etc. OW got an ego boost because an older many who was above her in class was choosing time with her over time with his own family.
It had nothing to do with skin, or youth, or even looks (want to see pictures of my FWH's OW?). It was about the ego stroking.
In fact, when I kicked FWH out, he went to live with OW. He than began sleeping with his former employee, who was 19, and even MORE over-the-moon over him than OW1 was. The 19 yer old weighed over 300lbs, and I don't even need to describe to you her body type. My FWH is a very handsome man. I have recently found out that one of my own "friends" falls all over herself in his presence. But, these OW stroked his ego in a way that I do not.
After R, my FWH saw a, IC extensively. One of the biggest issues he had to work through (which I wasn't even aware existed in his relationship) was the unknown (to me) fact that FWH thought I was "better" than him, and somehow projected that attitude onto me, and got it in his heard that I, too, considered myself "better" than him. It is my opinion that this dynamic exists in a fair portion of affairs, that there is something broken in the WS, under the surface, that the BS may not even be aware of.
Anyhow, that turned into quite the ramble. It's not our skin. It's not our thighs, or our ass, our our breasts. It's that when we look at our spouses, we see humans, where these young OWs see some sort of demigod.
(This is likely generalizing, but I see many, many parallels between your H's OW and my H's OW).