So maybe it’s just me but when I was watching the results for the best trick contest YYE just posted I thought their strings looked long. When I measure my strings I go by the waist to ground measurement. Do more advanced throwers lengthen their strings?
It’s really all about personal preference and style. The standard length people go by is the waist to ground. Some people prefer to use longer string for slack tricks, and more advanced tricks where it’s better to have more string to hit. Overall, it personal preference.
I cut mine to 1 finger above my belly button 
I pretty much like the stock length of YYE bulk strings, I typically use that length or close to it when I have to adjust strings unless I’m using loopers, but we’re not talking about that right now.
I’ve also found that some yoyos behave better with longer or shorter strings. My Decapod seems to work best for me with a shorter string than normal.
i Spread my palm open
put my pinky on my belly button then do floor to thumb.
and the bottom of the loop on my thumb.
I use full length YYSL.
I am 6 ft. and I use YYSL with about 5" cut off (fold at belly button, tie and cut). So, assuming Yonut isn’t 6’ 6", it really is preference.
So do I. I like mine reeeeaaally long.
I’m five feet seven inches.
I use YYE bulk poly mostly. I enjoy the length however when I throw things that involve a double or nothing (and similar) i feel like I need some extra length. I bought some YYF superlong string last week and did some testing to see where my sweet spot would be. I only need an extra 8 inches or so. Took me a few throws to get used to it. I feel like I’ll just stick with standard length until I start making string myself. Too expensive otherwise.
Kitty is nice if you want longer string on a budget.
3in. Above the belly butten