Question about men

My (35) last few relationships with men (37 and 47 year olds) they have had trouble getting/keeping it up. TMI sorry lol. What age do you ladies notice this starting to be a problem? The 37 year old- we’ve been on and off again since we were 20/22 and it’s never been a problem before, in fact quite the opposite. He’s always had a really high sex drive. Part of me thinks it’s normal but the other part of me thinks it’s me. I love him and we’ve really gotten more open with each other as time goes on and this time, we’re older and it feels way different. He wants to get married, have kids, etc. Is this common with men after 35 ish?