Depends on my confidence. If I am shooting a lot and hitting consistently good out to 40 yards, that would be my max on whitetails. On Elk I usually practice out to 60 but 50 or so would probably be my max. The longest bow shot I've ever taken at a whitetail was 32 yards at a doe, and I drilled her perfect. In other words, even though I may say that I feel comfortable at 40 yards, and had chances to shoot at that distance, I've passed those shots hoping for a better shot.
Your max should be the distance you feel comfortable/confident with.
Your max should be the distance you feel comfortable/confident with.