Florence is beautiful and she'll look 20 when she's in her 40s. Also, Britney looks her age she just has bad skin. Lately she looks like she's taking care of it though so that answer is invalid. Madonna looks her age too.
I'd really like to know what kind of 54 year olds you know.
I find that excessive/obvious plastic surgery usually ages someone, not makes them look younger, so I think it's fair to include Madonna in this. She looks older than Kim Cattrall who is two years older than her.