I'm modestly productive. I know a few exceptionally productive people. They did not learn how to do what they do, they just fell into being busy and didn't stop. Some of them attempt to push things farther(e.g. taking caffeine or pharma) but that is not the essential factor. The factors are more along the lines of personality, situation, and stress level. If they keep getting asked to produce something, and they really enjoy it, and it's not leaving them worn out at the end of the week, they can hold things there indefinitely.

IMHO, don't worry about quantity. Just focus on training and process. If you arrange your environment and daily activity in a way that leads to good work, it doesn't matter whether it's operating on cycles of six weeks or ten years. You get different kinds of work done on those cycles.