We had this discussion many times before. One year I did a thread asking for help calculating all the ages of the winners from the Major events. I think AtLarge came through and showed us stats for the US Open, WPA World championship, and maybe Japan open. The age was much lower than 30. This was even before Filler and Kaci came on the scene I believe, so the age would be even younger now.
I maybe used the word "peak" too precisely. I do agree players can improve a small amount in their mid to late 20's to early 30's. But that improvement is maybe to learn one safe every year they never saw before. Or maybe they are more seasoned in international competition, for example. But the physical act of moving the stick isn't any better. The physical act of moving the stick is developed and pretty much peaks by the time a player is late teens/early 20's. That pyhsical act of moving the stick is needed 100% of the shots. The runout patterns are also developed during this same time period. These two items, physically moving the stick and picking the runout patterns are 95% of the game. Yes, some of the other stuff might get stronger in the later 20's and early 30's, but its such a small part of the game compared to moving the stick and pattern selection, that even if a player improves those items, it won't budge their location on the pecking order.
Lets take the case of Corey at age 21. Maybe the only player in the country at that time that would have been a betting favorite over him was Archer. And guess what, 10 years later Archer was still a betting favorite over Corey. Also in the case of Corey he was probably feared more at age 21 than at age 31. Lets take Sigel and Strickland. Maybe at age 16 Sigel was a favorite over Strickland (as he was older). But by the time Strickland was 21 or 22, there is no way Sigel would have been a betting favorite. Maybe a pickem. Daulton vs Varner in Bank Pool. At Daulton age 16 Varner would have been the favorite. At Daulton age 21 it was probably a pickem. How about McCready since we have a personal line on him via Jam. At Kieth age 16 Buddy maybe could have given him the 8. At age 20 there is no way that would have happened.
Now, I will say the peak "range" of a player is about age 19 to age 35. During that whole range I think the overall speed of a player will be maybe within 2% or 3% variation. After that, things start to go south slowly. Not only for physical reasons, but also for mental reasons. The hunger is not there nearly as strong.