No limits at all . If I can hit what I am shooting at I take the shot. Conditions matter a lot more than yardage. A fast bow and a lot of practice makes a lot of difference. I see no reason to set any arbitrary politically correct limit on my individual capability.
If I question my ability to make a clean shot then I don't take it. If I feel confident in my ability to take the shot I do and I have learned after many years of hunting to accept whatever the consequences of that decision is.
I hear a lot about string jumping at further range. My personal observations after 57 years of bowhunting and several hundred kills is exactly the opposite. I have had more animals jump the string at close range than past 20 yards. A lot more in fact. Of course if you limit yourself to taking under 20 yard shots then you could not know that . Grin.
God bless you all, Steve