I used to say exactly the same thing when I was 16, and I'm sure you got the same reaction I did from people; "Oh, you'll change your mind when you get older, and meet the right man". Well, I've been with the right man for 20 years, I haven't had various parts I would need for the endeavor for the past three years, and I'm 51 - how much older do I have to GET? :)
They told me I'd like olives "when I was older", too. That is beginning to happen, but I figure I'll be at least 60 before I stop picking them off of pizzas.
I get the "why do you have so many" or "are you done" line. How about we kill two birds with one stone. When you are asked you can say someone else took care of your quota and I will say I am evening things out for people who didn't want to have children.
I am thankful I married a man that did not want children either.