I live just outside of Denver. Even my ridiculously in-shape younger brother, running track for Kansas State, came back over the holidays to go on a backcountry hut trip with me and a few friends. He didn't acclimate/hydrate for a couple days (1 minimum) in town, and went right up to the high country. He was out of commission for about 4-5 days with some altitude sickness. It is easily avoidable, just plan the couple days into your hunt in advance, and don't drink (or at least don't over-drink) for first 4 days or so.