Very dependent upon the local terrain. In some areas, you’d have to cover a lot of ground to gain 2,000 feet. In other areas, it’s hard not to cover that in a mile or 2. That being said, gaining more than ~1,000 feet a mile gets serious, especially at elevation. So, 6 miles and 2k feet of climbing is one thing, 1.5 miles and 2k feet of climbing is another thing entirely and may take longer than those 6 miles. If it’s off trail, it could take many hours. None of it is unrealistic across the board, especially if there is a trail, it but could be very difficult for a flatlander at elevation, especially if you’re doing it day after day.
Mtn Biking trails in Durango, I average about 200 feet of climbing per mile. Go up the road 30 minutes North into the heart of the San Juans with a starting elevation of ~3,500 feet higher, and it’s not uncommon to average closer to 300 feet of climbing per mile. And that’s on trail that tends to be the past of least resistance. Never tracked it like that for elk hunting, but expect to gain a bunch of elevation out of the gate and 1,000-2,000 feet per day after that.