I think sixties is probably getting towards "too old" in that you won't be able to see your child fully grow up. My best friend's dad had him when he was 62, he's now 86 and my friend knows he likely isn't around much longer. My dad had me when he was 25, but he had my half brother 28 years later. He's an older dad now but still healthy, perhaps not as much of a runner and physically strong as he used to be, but I can see how much he loves being a father.