It's really depends.
On what sort of relationship, kids etc.
I know someone who started going out with a 24 year old, she had 4 kids and couldnt have anymore. She was 36 at the time.
He insisted he was happy never having kids etc. The marriage was good until he hit mid 30s and realised he did want kids. He tried to ignore it. She had grandkids at this point. She tried to ignore that she knew he wanted them and she couldnt have anymore.
There were a few problems. She hit menopause (which seems to be a hump for some relationships anyway) and didnt hee sex drive took a huge hit. He was mid 30s and though he tried to be ok with the no sex, he struggled (as most of us would I think) he never cheated, but it was a problem. The kids issue became a problem. She then started believing he would leave her for someone younger able to have kids, cheat on her. The marriage ended up crap. He didnt cheat and wanted to stay in the marriage. But the problems became too huge and they became miserable. Neither bad people or did anything wrong as such.
After the split, she actually got back with an ex her own age and same stage off life. He did meet someone else and have a child but it took 6 years to even date as he did still love her.
I know this is one example. But as a single mother in late 30s, I have been chatted up by men in their 20s who say they dont want kids. I just think that opinion can and often does change.