11 year old won Korean Nationals

The optimum age is definitely young, probably like 10-20. You learn and pick up things the quickest when you’re young, also you generally have way more free time to practice

The ideal time to start perhaps. I have seen several scientific studies indicate that the human body peaks at 25. Experience and skill would probably put the “peak skill” level closer to the 30 mark until the physical limitations kick in. The major factor in this comes down to time to practice. In high school I had a ton of free time. As an adult I have little. It is also impossible to make a living being entirely just a yoyo player.

does gentry stein have any jobs other than yoyoing i didnt know about?

Sells a signature yoyo that he helped design and has a clothing line (Icon). My point is that you can’t make a living on competitive yoyoing entirely, you need to do other things since the prize money is so inconsequential.