Your maximum hunting shot should be no more than 80-90% of your consistent 8" centered group on the target range WITH YOUR BROADHEADS. That's my opinion, I'm sticking to it. More variables in the field. I practice out to 70 occasionally, 60 regularly - my longest hunting shot to date has been 42 yards (kill, 6pt bull). Realistically, I'd stretch that to 50 under perfect conditions. Maximum range without a rangefinder is much less.
Three years ago I spent 3 hours within 70 yards of a bedded 7pt bull with cows, hoping he'd come my way when he stood - no way to get closer. I thought about that shot hundreds of times between 10:00 and 1:00 - and figured it was about 2 in 3 I could kill him. When he stood up, I didn't shoot, and he didn't come closer. I'm not claiming any high moral ground - I've learned the hard way through the sick feeling of losing animals, and the worry and subsequent elation of tough recoveries. There's enough potential for that anyway, without pushing the limits of your abilities.
I think most of the ethical among us - gun or bow - eventually learn that humbling lesson by losing animals after launching a hopeful shot. Kudos to those few who know themselves and their abilities to reach that point without learning it the hard way. I have nothing but contempt for those few who continue to fling and wing, year after year, with little concern or regard.
My actual field shots this year included a deflection at 41 yards (8" window between 2 tree, miss); mis-judged "30" yard steep downhill shot the day I left my rangefinder at home - 36 yards, miss under the chest; 42 yard miss that looked and felt perfect - fortunately, we were able to confirm the miss by watching the buck after, as the arrow disappeared into the snow; and a 24 yard kill. Yet, I can shoot 3-5", 3-shot groups with my hunting arrows at 40 yards with absolute consistency.