The tendency for creativity to happen when you are young has little to do with being young, and far more to do with being fairly new to an area of work. Creativity peaks after a few years of practice, in almost every field, because when you start out you do not know enough to be creative... and after some number of years, you get set in your own personal ways of practicing your work/art. There is a peak between those two points when you know enough to be competent, but aren't yet set in your personal ways and styles. Yes, many people hit that peak when they are young. But they also hit that peak when they are older, and try something new.