You know, I have watched alot of hunting video. I have seen some of the "pro's" miss a deer or maybe not make such a great shot on a deer, even at a closer range.Like mention, there are alot of things that can go wrong the farther you are from the deer.IMOthe farther the deer is, those chances of something happening go up.
I like to stay around 30 to keep those chances as low as possible, because I don't only owe that to myself!
Crutch