I think if a man is going to be in it for the long haul, he'll be in his relationship before he reaches 30. There are some good men around older than that, usually because they've been crapped on by their partners and are starting over
Looking at my close circle, I see DH (we've been married 25 years and I love the bones of him, think he feels the same way about me), DH has 3 brothers - one has been married about 10 years longer than we have, one a couple of years less. Both relationships seem strong. Other brother is single, in his sixties, never had a long term (more than 3 years) relationship. We think he's a good bloke, would make a great husband/partner but he could be perceived as a bit boring - for boring read reliable, steady, honest. He's also a bit shy. His relationships usually end up with the woman leaving for a 'bad boy', who causes misery and mayhem and she the cries on DBIL's shoulder....
Then we have BFF and her DH - been together since early twenties, had a bit of a wobble when DCs were small because it was tough, but struggled through for a few years and are brilliant together. It helped that even when things were tough her DH pulled his weight.
DSis - divorced from her manchild, unfaithful DH and very happy with a guy divorced from his selfish, manipulative DW. She didn't like the fact that he couldn't support her 'ladies who lunch' lifestyle.
Conclusions - there are definitely many decent men out there. You just need to do your homework.