It really depends on what type of artistic person you are. You can create your best work in your youth, or you can create your best work within a few years of your death. David Galenson did a lot of research on this topic, albeit in the world of painting, (later he investigated music and poetry). He plotted painter's ages and when they did their best work. He determined "best" work based on auction prices and how many times a particular painting was shown in art history text books. The two ends of his spectrum were "conceptualists," artists that peaked early and "experimentalists," artists that peaked later in life. Google is your friend if you want to learn more about this concept.