Isn't the normal response (from older ladies at least) to say "I'm as old as my tongue and a little bit older than my teeth." Which is wrong anyway because the so-called 'adult teeth' are actually present from birth, but buried in the jaw - thus making the ladies (and gents too) the same age as both their teeth and their tongues. I guess this kinda defeats the purpose of the answer though, they might as well say "I'm as old as I am."