Very important. Check your zero of your rifle apon arriving in the altitude you will be hunting at. At higher elevations your rifle zero will change. If your say at 4000' ft and you hunt at 9000 ft or above your looking at 2" increase of height of your zero at 100yds. That becomes 5" high at 100yds compared to 3" high. And if your going the shoot past 200 yds these factors greatly effect your shots. I would recommend using the 200yd zero and read those trajectory charts for your particular load and know them by heart. At higher elevations your bullet drop will be less than most printed tajectory charts because of less air density. But up to 500 yds the charts will be within 6inches at five hundred yards if the rifle is sighted in at that elevation.

There are high elevation charts out there you just have to go find them.

I would pratice making some long range shots and see how well I actually did then I would set my limitations accordingly.