Lots of miles. I would rather combine Yellowstone with eastern WA and OR in the fall in one trip and combine AZ, NM, and southwest CO into one trip. We did a Yellowstone to Zion trip last year and covered 3600 miles. I would not do it the same way again.
I was in Death Valley in late March many years ago and I was never so cold with the extreme wind chill. Grapefruit sized rocks were being blown down the highway in the high winds.
We are planning a Nor CA trip in May along the coast and inland into the gold country covering about 1800 miles in total. We will be in the Yellowstone area in late August. Another trip planned for mid-November will be to NM and Bosque del Apache for the sandhill cranes and then up to Taos and Santa Fe and back through the Chaco Canyon and Ship Rock, Monument Valley, and the Grand Canyon.
From the itinerary you can see our travels are oriented largely toward wildlife and landscape photography. A crew cab or super cab 4WD truck with a camper makes a great photography base. Sure beats the heck out of Ansel Adams old Caddie with the platform bolted to the hood.