That's a long trip from the White Mountains! I've never done the "go west" thing, always north-south, but a co-worker just came back - Grand Canyon, Hoover Dam, Vegas, A LOT of great places. He was a little over 8 weeks in all, but I don't know what pace he took.
I always prefer a 300-350 mile a day itinerery for a fairly casual vacation, and often used CAA (AAA in the states of course) to get those great Trip-tic maps they prepare, spelling out all the spots we feel we need to hit.
But without personal experience, I can't give much good advice. I'm sure some of our members can though.