Kirk - drive is easily doable in a day - about 750 miles...from South OC. I've done the drive into Grand Junction from here a couple of times - 800 miles. Always iron butt it home on Sunday. Try to get out of Moab at 5 or 6 am to beat at least some of the Vegas traffic home. Still sucks when you hit the PRK border and towing a trailer, I'm stuck with the trucks!
I did the drive in October only we went through Zion on the way to Moab. Right now I am planning to Leave SoCal early morning Tuesday and depart early Sunday to head back home. I have Wed daytime free and Saturday all day free for side treks based on the runs I signed up for.
The drive from Zion to Moab sucks in the dark fyi. Poorly light two lane roads in thick deer country.
PITA to be stuck with the truckers in the right lanes. It's only in the PRK. Nevada, Arizona and Utah there are no restrictions on trucks or vehicles towing trailers! I can do what the rest of the caravan is doing w/o worry.