We met a couple on a tandem doing the same thing, only west to east, in 2009. As I recall, they were cranking out some big miles (80-100 per day) to meet their schedule. Their light load (compared to us) allowed them to make those miles, at least as far as Montana.
That couple had motel reservations clear across the U.S.A. In the east, I suspect that was overkill; in the west, not so much. There's only so many places you can stay out west, and they get full on summer weekends. For the most part you should be able to make it within 75 miles per day. I think the Mazama to Concrete, WA day might be a bit longer than that, but you should be in really good shape by the time you hit Washington Pass going west.