Doing about 10 miles a day is quite reasonable, even with 3000 feet gain. Trail strategy while hiking will help a lot, in addition to pre-trip training.

1) Get going in the morning. Become an efficient camper and get on the trail by 7AM, no later than 8AM. This is particularly important in the Rockies because of afternoon storms.

2) Start slow and steady and keep a constant heart rate - this means slowing down going uphill. I usually speed up by mid day and then slow down again at the end.

3) Keep moving, with about 5 minutes rest every hour. Nothing slows down the entire day like 20-30 minute rest stops! You should set a pace that is comfortable for all day.

4) Keep your map (or GPS) out handy. Nothing wastes more time and energy than getting lost.

5) snack all day instead of eating a big lunch.