The reason I do,and also reccomend that scope stay on bottom side of magnfication is simply in case of close/running/fast shots-your field of view will be largest and thus,easier to pick up deer in sight picture. If a deer is spotted at longer range,it'll usually be there long enough to zip scope power up-if it don't-you didn't have a good shot in 1st place. NOT a old wives tale.
ORIGINAL: The Rifleman
Power turned down for hunting?
I keep my scopes on 5x for hunting and turn them up a I need it.
Keeping your scope as low as possible is also an old wives tale.
All you have to do is sight it in at the range that you think that you are going to shoot and it will be just fine.
There is no use sighting in a gun for 200 yards if you are only going to shoot 50 - 60 yards. That is how a majority of deer are missed each year.