Answering from my personal view, my knowledge probably peaked a few years back when I was playing more One Pocket all the time by traveling in about a 100 mile radius. Because I think for you to take advantage of your study of the game in order for it to peak, you have to be playing a lot of One Pocket. Because it only really peaks if it is a practical knowledge based on melding your conceptual knowledge and your experience. We've all heard the comments about real knowledgeable players, like Grady for example, that "he has forgotten more about One Pocket" than we will ever know
. I think your knowledge peaks when you are immersed in the game -- so it isn't really an age thing, it's more like catching a wave.
Most great players, when you look at their trajectories, they grew the fastest and often caught their peak wave at a given game when they were immersed in good competitive situations that included other like minded players -- not in a vacuum.
You can see that in players too -- of different ages. Look at Shannon Daulton -- knowledgeable well beyond his years at 20 years old because he was immersed in the game early. Whereas Efren came to the game late, I think his knowledge and skill intersected about 5 years ago, at about 55 years old.