Just to put the OW age / relationship thing into perspective a bit...
First, understand that APs (affair partners; the spouse who has an affair) often "affair down". ie. the OP is somewhat below the maturity, looks, age, perhaps even financial status or potential of the LBS.
Also, if your H is MLC, he may be acting younger than his age. Trying to be a party animal again, or something. Which might mean he has an OW who is of similar "age mentality".
My W is 47. She's been surrounding herself with people who really, really, really like to "party". ie. drink hard, stay up all night, and do that as often as possible. This includes OMs who might otherwise appear mature and normal, but "let loose" every chance they get (ie. all weekend, every weekend)
OK, I'm exaggerating a bit perhaps, here... I'm saying it this way to make a point, of course.
Also, her female friends are significantly younger, like 20 years younger, so about the same maturity age. And also includes her early 20s niece.
So my W is trying to fit in with that group, including spending many weekends at the local hotel / pub with these people.
I do like doing that from time to time, sure. I just know that's not "my place" any more. I'm 45... I just can't do that any more and really have no desire to... not as a regular...
Anyhow, my W's niece and one of my W's young friends went out one night clubbing, without W...
And W was apparently quite offended about that. I don't know why it would be offensive for a couple of 20 year olds to go clubbing without the 47 year old mother of two.
So again, to put it into perspective... my W might be fun to party with, but the reality is... even her support group isn't seeing my W the way my W probably thinks of herself... as some 20 year old chick, living the dream...