Have you ever wondered why so many famous musicians, writers, and creators of all types have been one-hit wonders? Let's broaden that thought to say that creators generally do their best work during a phase of their lives, and that phase usually corresponds to youth. What's up with that? Why doesn't experience count for more than youth? I'll list some obvious reasons just to get them out of the way before telling you what I think is really happening.
Focus. When you're young, you can work intensely on a project and ignore everything else. As you get older, that becomes nearly impossible. Over time, your life naturally becomes more complicated. Your brain and your schedule accumulate so much clutter that concentration simply gets harder.
Risk. Young people can take bigger risks because they have less to lose. And the young are probably wired for riskier behavior in general. Big successes generally follow big gambles.
Hunger. You're always hungriest before you succeed. Everything else being equal, the person with the greatest motivation will come out ahead.
Youth is Interesting. When a young person creates something great, the public is interested. Humans are wired to be more interested in youth. Hypothetically, if your grandmother wrote the best song in the world, no one would care.
Creativity. Young brains are more creative. I'm not sure that this particular advantage is big enough to overcome the extra skill and experience that a creator gains over time.
The Halving Effect. A publishing rule of thumb is that a non-fiction author will sell half as many books with each successive effort. An author's first non-fiction book is generally the best ideas of his or her entire life. The second book is the stuff that wasn't good enough to be in the first book.
Some non-fiction writers defy the Halving Effect. And the biggest names in fiction do it routinely. When you see that happening, it often means ghost writers have taken over the heavy lifting while the famous author is more of a project manager.
Drugs. Young people do more drugs than older people. And artists probably do more drugs than the average young person. That might be a correlation without causation. I doubt there's a scientific study on that topic.
Comparison Effect. If an artist produces something great, followed by something that is 90% as great, the second effort will register as a disappointment to fans. The Comparison Effect works to the advantage of an artist such as Britney Spears whose early fame exceeded the quality of her music. She had lots of room to improve her music and surprise fans on the upside.
Fan Fatigue. If a creator keeps mining the same vein, it all starts to feel the same to fans, even if the new work is as good as the old. If a creator tries to game the system by moving to something completely different, the Comparison Effect kicks in and fans say he should have stuck to his "day job."
My personal view is that one-hit wonders exist for the simple reason that you can only do one best thing in your life. If that one best thing happens when you are young, you might be lucky enough to be a struggling artist who can capitalize on it. But if your one best piece of work was going to happen at age 60, again by chance, you'll never find out. You'll probably be forced to change careers decades before your luck has a chance to happen.
This is a variation on the observation that you always find a lost item in the last place you look. It feels like a coincidence and yet it can't happen any other way. A creator who doesn't find success early will likely change careers. And for someone trying to make it big, anything less than a great effort early on probably won't get traction.
In this context, your best work also involves timing. If someone wrote the best hip hop song of all time in the Middle Ages, he had bad timing. A creator's best work is usually a lucky intersection of timing and talent. And by definition, you only get to have your best timing once.
When it comes to creativity, younger is probably better. But it might be overrated.