Another thing to consider is being able to stay in control of your shot when an animal is in. I had a buddy miss a bull elk four times at 20 yards! Two over the back, two under the belly. When he first pulled back I could here his arrow rattling on the bow. It was a small rag horn, but it rattled my buddy. He simply wasn't prepared to make the shot, and was lucky he didn't wound the critter. The best method for staying in control is to talk to yourself when the critter is in. Be calm and discuss the shot with yourself, once you can calmy execute a shot, then you can worry about distance.