I come from a very structured back ground of practice from my high school and college wrestling days. Practice must be perfect, and I do subscribe to the idea that poor practice is counterproductive. I do, however, believe that to commit proper shooting form to autonomous muscle memory it must be done PROPERLY, for as many repetitions as absolutely possible. You will hear of guys that just shoot one arrow a day, or session. In my mind that isn't practice, that's simulation of a hunting scenario (also a useful tool). I believe you should shoot as many arrows as you can and still maintain proper form. For me, I can shoot 100+ arrows before I notice any fatigue. I will also mention that this is a result of shooting a lot for a long time to build up to that.
One mans opinion, hope it helps.
Jake