When I was young, and even into my twenties I could never wait to be older, and look older. I used to look at photos of mature French ladies in magazines, who always looked so stylish and self possessed (yes, I know it was marketing) and think that would be much more preferable to youth.
As women age, they often develop a self assuredness and confidence, and a comfort in their own skin that makes them shine more brightly than any youth or beauty ever does. Its that being at peace with yourself, and accepting yourself which makes people seem beautiful I think. That true inner self confidence and self worth, and not giving a fuck, is impossible to mimic.
So I suppose that's a flowery way of saying that despite age, I think all women look most radiant when they are happy just being themselves without bending to anyone else's ideals. It sounds pompous to say, but I really don't think it has anything to do with physical looks.
Some younger women have it too, but I think it often takes life experience and whole lot of being trodden on to truly develop the not giving a fuck. and to truly love yourself, faults, flaws and all.