I think that is the age that you have just mastered an art, but it's before you've done it long enough for people to lose the feeling of novelty in what you bring.
I think it's less that you lose what makes you good is what's unique in you, but once that's out there it's not like you'll really gain more individuality, but this statement just heads into nature vs nurture. I could however name tons of people who've remained awesome there whole life, but unless you really want to take large random samples of artists here, we're going to have nothing but biased preservatives and anecdotal evidence. That however requires the work one would put into a college or uni paper, and I do not feel like putting in those hours. If you feel inclined to, please do so.