You have to turn it off when the object isn't near your camera view. You wont notice this from a distance anyway. Without turning it off though, around 15 highish poly animated models(8k+tri) onscreen at once, the cpu is 10%-15% increase and fps drop is up to 15-20. I don't know if its the same with non animated stuff, I can't get it to work to test. Haven't tested with low poly models either. Should be pretty good performance unless your making a game with 50+ enemies on screen at once, which would probably still be okay with lower poly's and good optimization techniques.