I practice out to 70 yds because that's all the pins I have. (30 - 70). I keep my first pin set at 30 yds because the difference at 15 an d 20 yds is minimal from my Martin Onza III Pro. The reason I practice at these ranges is that any errors in form will be greatly magnified and it also makes those 15 - 30 yd shots much easier because you are more confident. I'd have to sit and count all the deer I've taken with the bow. But what I can tell you is that all but 2 have been shot at 20 yds or less. The 2 that were taken at longer range were 35 and 43 yds. I feel confident out to 50 yds but the animial has to be totally calm and preoccupied (eating or other). Even with today's super fast bows, it takes enough time for an arrow to reach a whitetail at 50 yds out for it to react and duck or wheel before the arrow gets there.
People say that a deer ducks the arrow. But this isn't naturally true. If you've watch such an instance in slow motion, what the deer is actually doing is dropping its front shouders as its first motion to flee. Think about it. What do you do if you're going to jump? You flex your knees as the initial movement. Same thing with a deer. Most hunter know this but I just want to let you, the new guy, understand it. So even at 20 yds, don't shoot at an alarmed/alert deer. Just sit tight and let it calm down. The tail flicking side to side is a good indication the deer is becoming calmer.