I've taken over 40 animals with my xbow, not that that makes me an expert, and all but 2 of those kill shots were under 25 yards. One was 27 and the longest was 37. I took the 37 yard shot because the conditions were IDEAL. There was a crusty snow on the ground, the deer had no clue I was in my blind and by chance I had practiced that 37 yard shot, I just happen to have had a target set up in my back yard and for whatever reason it was exactly 37 yards from my carport, I knew exactly where to aim and sent the bolt square thru his heart.
Without the snow I would not have taken that shot, the snow is a great help when it comes to a marginal hit.
All that being said ETHICS and MORALS should be an equal if not greater deciding factor on your max shooting range that the effectiveness of your weapon.
Good luck,
xbowbarry