Newton achieved much of his success, in his mid-twenties. Back at his mother’s farm after his University had been closed because of the Plague, in an incredibly brief period of about eighteen months, he did fundamental work on developing calculus, conceiving the law of universal gravitation as well as working on key concepts for a study of mechanics that would apply throughout the universe.
Einstein, in a period of under eight months in 1905, again in his twenties- and while putting in full days at the Patent office where he was employed-came out with his first theory of relativity, the equation E = MC2, as well as his work that helped lay the path for lasers, atom bombs, space travel, computer chips, key aspects of modern pharmaceutical and bioengineering industry and all Internet switching devices.
Mozart in his teens had performed in many countries, but it was in his twenties that his composing talent blossomed. He started writing operas in German, a novel innovation as the tradition up to then was to write in Italian. He was keen on new instruments - he wrote major works for the early piano (which was smaller than the 19th C piano by at least two octaves). In his twenties, Mozart also composed horn and clarinet concertos for musician friends who specialised in these instruments but had no music to show off their skills. They are still the definitive concert works for horn and clarinet.
In my twenties, I became skilled at whistling in the bathroom, discovered that I could grow a beard if I didn’t shave for ten days in a row, managed to drive an Ambassador car up to third gear, started using spectacles, figured out the difference between billiards and snooker, learnt how to wear a tie and still breathe and as a traveling salesman was a storehouse of knowledge on the hundreds of railway stations and bus stands in South India, especially with respect to the location of the toilets in each of these places,.
So, as you can see, there is a definite pattern. So many creative geniuses have been most productive and prolific in their twenties.