I agree that it might be better to go Northern route and return via southern!

From November to Mid-Dec in Yellowstone. I don't think any of the park concessions are open at all during that time-so not sure about the roads at that time either.

8000 miles means you have to drive 285 miles for an average day. Whoa, sounds like very little time to actually see a thing, IMOP. I think for 7000 of those miles you might could average 70 MPH, but for 1000 of those it might be more like 30 MPH. So you might wind up about 55 MPH. All those National Parks have low MPH. Now if you happen to run into snow, well then that can be 10 MPH.

I like winter places too, but it just depends on what you are doing. I am not opposed to driving in winter, but I don't want to get somewhere and then half of it be closed. Snow Skiing in Colorado(not great early though) sounds fun-The main two hikes in Zion not doable doesn't sound fun though is my point.

I drove 300 miles today and had plenty of time to "do and see" stuff. I agree with posts up thread that suggest doing your major sight-seeing on the way east and then make better time on the way back home.