He married at 20, a woman who almost 40 then. I've only known him for the last 5/6 years, but understand it created quite a stir at the time.
They've been happily married 30 years, he's in his 50s and she's approaching 70.
He's a fit and active 50 something, she has (in his words) become an old lady. He still speaks of her with enormous fondness but he is finding a freedom in middle age (now DC are off their hands and his career has settled into that life where you can earn well without working so hard) and wants to get out and live a bit. She doesn't want to do anything or go anywhere, to the point that she's refused to renew her passport and he sees it as "success" if her persuades her to go for a short walk. He was recently at a party, she refused to come, but also was not happy that he went.
I be clear, I have no designs on him, but he's asked. I've also never seen any signs that he's looking elsewhere or messing her about.
She's fit and well, she could get out more, but doesn't want to. He has tried going off to do things on his own, but she doesn't like that either.
What I've actually said to him is that if you want to fix your marriage, discussing it at length with another woman isn't likely to help, but I'm kind of thinking don't waste these years while you're in your prime. That's probably what I'd be saying if he was a woman.