Apparently, not enough. I have missed the same buck twice (2 different occasions) standing in essentially the same place. Both were very near misses, but oddly enough, neither shot really spooked him. He just looked around and trotted off.
Like many others I fall into the error of practicing less during the season, because I am in the stand as much as possible. After the season, I start in January getting ready for 3D. Then I shoot 3 or 4 times a week, loosing 40 to 50 arrows pers session. Range varies from about 15 to 30 yards.
This year has been a problem. I hurt my shoulder last May, and it still is not healed completely even though I am shooting a lighter bow.