Well, the youngest prossie I had was 18 and still used her real school uniform. Hmmm, a bit pervy. Anyway, she was beautiful, firm fleshed and lovely; but just an average punt, though.
The oldest; 40, but In very good nick. Mind bogglingly dirty full on punt. Erotic, filthy, memorable.
So I'd say a good punt is down to a variety of factors of which age is just one.