Ex.: Do anything which gives you joy: you're not getting any younger!
Ex.: James is only 12 but he's so mature: he has an old head on young shoulders.
Ex.: That story is as old as the hills
Ex.: She is 53 but she looks younger: she doesn't look her age!
Ex.: My grandfather tells me that the youth of today are very different when he was a lad.
Ex.: No matter how old you are if you stay young at heart!
Ex.: You don't need too much explanation about that: you are old enough to know better.
Ex.: My grandma still loves going to dance: she doesn't feel her age!
Ex.: Act your age! You aren't a child any more!