To me the case for marrying and having children when I'm not too old is quite simple really
The older you are the higher the risk of having children who are not healthy. Having children who are not healthy is a major burden on your life, a burden much heavier than marrying too young or not having the best career. This is it, the rest of your life is tied up in responsibilities to that child (depending on severity of their condition). Imagine having a child that you know will never make it on their own and will require you for permanent assistance? Some people ask what's the difference between 40 or 50 years of marriage? The difference can be between 0 or 40 years of extra maintenance as payback for having that extra time when you are young. How happy would you be to spend your twilight years, the time when you are most vulnerable nursing your children? People who are pushing marriage into their 30s and having children into late 30s or early 40s should really stop and think about the risks involved in those decisions. Because the risks grow by the years and sacrifices they will have to make if those risks eventuate are enormous. Personally I'd like to have children by the early 30s, some of you may think that's too young, but I think it's already pushing it.