I need help and advice.

I’m currently 29 weeks and 1 day pregnant with a baby boy. My fiancé and I have known each other, since I was 18 (now I’m 21) and he was 34 (now he’s 37). Even though we known each other for about 2 years we’ve been together a year and 5 months. He already has 4 kids from a previous relationship that I love them like their my own. I know he’s going to be an amazing Dad to our child, because he’s already is to his kids. We’ve planned this baby, but eventually I would want another one. I’ve always wanted a big family with 8 kids, but since he has 4 I’m happy with that. I asked him can we have one more, he said he thinks he’s getting to old and 6 kids is a lot. He said just wait in 10 years when his kids gets older and our child going to be 10 years old and he’ll think about it. I’m just concern, since he’s going to be in his late 40s and I’m going to be 31 years old will he still be able to have more kids? Did y’all had a kids at an late age? Did your spouse was older when y’all conceive? Should I be concerned?