One of my old roommates and neighbors once did a run in an M923A2 from Barstow, CA to Phoenix, AZ to Portland, OR to Fairbanks, AK...pretty much nonstop. I think the PDX>FAI part took them only like 3 days, driving pretty much 24/7 taking turns.
In a 5 ton, you have to pace yourself. 250 miles a day and motel'ing it at night or stopping at fellow enthusiasts' places or the homes of friends in the states you pass through and it can be quite fun. (Did that myself riding shotgun with a fellow member here). Ramroding from SoCal to interior Alaska and you'll have your co-driver swearing they'll never get in one of these again (Neighbor adamantly swore they'd never drive one of these again as I recall).
You can sleep in the cab or the bed but you'll want motels for showers and better beds. One night freezing your toes off in a M925 cab at 31 degrees with inadequate textile covering items and you'll be willing to spend the $100 for a motel and a hot shower.
It's still worth it despite the toll on your lower back.