I'm 28 and have a 2-year-old. People ask us all the time when we are going to have another. It gets a bit awkward because I have certain medical complications that make it highly unlikely that I will get pregnant and if I do, highly unlikely to carry to term. I hate being asked when we will have another because we would love to have another - just don't know if it is going to be possible and it is always awkward trying to find an appropriate answer to that question.
In any case, I wouldn't consider myself too terribly old, but I have discovered great things about the aging process I'm going to give my top 3 things about getting older:
1. I was always the baby of the family (including siblings, cousins, etc. and on both sides of my family). Now, however, I am an adult and am actually able to have a say in family discussions. Also, I get to have a say in whether or not I attend obnoxious cousin's birthdays and other get togethers.
2. As SaraJayne said, it's nice not to have to worry about what other people think anymore. Personally, I feel that I have an amazing life with a husband who treats me better than royalty, a beautiful daughter, and am very close with my immediate family and my in-laws. If someone doesn't like the way I live my life, I have discovered I really don't give a flying pancake. Those people don't matter. And the people who do matter know that I am enjoying my life and doing the best I can with what I have.
3. I get to wake up on a random Saturday morning, roll over and tell my husband that I would like to drive an hour and a half to go to the zoo, and we can actually do it. Tell me if that was ever a possibility when you were a kid!
Worst thing about getting older is easily watching my daughter get older. I actually miss sitting on the couch, watching The Golden Girls on DVD, and nursing her.