Well, David informed me that I was old when I turned 20, so you take much longer to be old than me. :) He felt that if you decide you're old earlier, then you're done with your mid-life crisis earlier and don't have to worry about any big number birthdays as well as feeling that he'd always felt you must be an adult when you turn twenty, and therefor, old.

Happy Birthday! And have fun at WorldCon.

Heathah