I had my second ones done for my 13th birthday, didn't hurt then either.
I wanted my daughters done when she was a baby but DH did not. He wants then done when she's older. She's 4 now, and I think it's too late, she'll have to wait till she's a fair bit older. It's much easier to get it done while they are young.
DD (28/09/03) & DS (05/06/07)