Hmm, I find this convo interesting. I agree on the point of keeping your options open. Not all Mule deer stay or even live high, my largest mule deer (during Bow season) came at a measly 6,800 ft in the sagebrush. this buck had the opportunity to be high as well. Deer like humans can be unpredictable. I would try and scout all elevations and be prepared to hunt where you are seeing the animals! Just my two cents! Best of luck to you!
You are correct, deer can be at any elevation in the early season, from down low around town to the mid elevation quakes. My experience is that a higher proportion of the biggest bucks live in the high country. Search the low elevations in that country in September, then do it again in December. . .