Be sure to correlate your route plan with the topography. YOU may be able to do 20 mile days, but the terrain ahead may disagree. You will lose all of those encounters, especially where you find yourself going uphill on the "V_'shaped tread made by the mountain bikes.
FYI - mountain bikers can be very helpful folks. They are a great source of water and rides. They can also be virtually silent coming up behind you. almost got knocked off the trail coming down into Breckenridge.
Just as hikers must yield to stock, bikes are required to yield to hikers. However, when meeting one struggling uphill as you descend, have a heart, be polite, and get out of their way. It's REALLY hard to get a bike going again uphill from a standing start. The Trail Gods will give you karma points that you will need later, often desperately.