Approaches differ today. My group (guys I hunted with), practiced a lot out to 400 yards;at 500-600 we also shot and knew what to do....if we needed to,like a previously wounded animal,or something very desirable with no option to get closer.Generally there was time to ponder this type of shot,and it happened infrequently,and for some,not at all.
It's more a question of being certain of the shot,and the outcome.
Today,guys are mesmerized by the sheer technology of the ability to hit a lot further...but from what I see, they still don't have it "licked".
There are still humans behind the rifle,still problems of wind(what it's doing "over there" versus what it's doing closer;advocates like to refer to this as the art form of LR hunting, or "calling" wind....this seems to me a euphemism for wild ass guessing)....mirage,springy erectors,animals taking a step or shifting slightly at the break of the trigger(unlike a steel gong),less than perfect bullet expansion at distance....maybe none at all.
Couple this with a frail,error prone human making these judgement calls and the further away an animal is, the less "certain" things become.
It ain't easy and it still ain't rosy; when I see experienced match shooters with years of competition under their belts refrain from this sort of shooting (on animals), I have to wonder what chance anyone with less experience has for pulling off a cold barrel, first shot solid chest hit at any great distance. I have met very few people truly capable of it that i would bet any money on...and one posts here.But he has a lot of experience at it,not just on targets but animals,too.
It's funny that almost all the most experienced folks I personally know at LR shooting are the one's that avoid it on animals.They have years and years of competition experience and know how many things can go wrong at 600-1000 yards.
I think the ethics very much enters the picture.
I like to shoot at great distance...it's fun.But the handful of times I have had to kill something at beyond 400 yards,I really did not find it particularly exciting.
Like Johnny B said it was more like shopping, or more particularly for me, just a job that had to get done.I did not get much thrill out of the events.
One last point,then rant over....a mature mule deer buck has a "flight awareness zone" of about a half a mile If he does not like the looks of you, he will leave,undetected,or otherwise avoid you and you will never know he was in the neighborhood. Getting within 300 yards of a truly large mule deer is not an easy thing to do...they got your number.
If he does not like the looks of you, he will leave,undetected,or otherwise avoid you and you will never know he was in the neighborhood. Getting within 300 yards of a truly large mule deer is not an easy thing to do...they got your number. 
