Depends if they are engaged or not and how taxing it is. People can play MMOs or MOBAs way past 40hr/week and they don't all have a huge performance dropoff. They are probably more prone to RSI and stuff at more hours though.
I wouldn't be surprised to see a productive 100hr week in some kind of MMO player.
I wouldn't be surprised to see a productive 100hr week in some kind of MMO player.