Very rare imo. I tend to notice their skin first. No matter how good they look, the skin is usualy a giveaway. Exceptional genes SOMETIMES postpone this, but a silky skin of a 20something is one of the best things of a young female.
Men are blessed regarding this, while women tend to get all the cards at once, from a get go (if good looking) it all tumbles down very fast down the road, while men just keep lookin good (again - if good looking) some to their ancient age.
Madonna is fighting a good fight, I love her young mind. Sad really, she's doint everything and anything to keep her body young, she loves her life/job obviously and it must be hard. The body is holding up well, the face seems to be an issue for her.