What accuracy/grouping size will satisfy you on 70m/77yd?

Hi snipers,
I'm just wondering where is your border of beeing satisfied with your airsoft sniper gun. When is the moment when you can say" It's good enough, I won't tuning it anymore". What accuracy/grouping size in example 70m/77yd will satisfy you? We talk about good conditions without wind, warm weather, static position. 15cm? 30cm? 50 cm? Cheers!