It's no problem to do that distance as long as you're up for it! Most people can tell when they are getting either sleepy or fatigued, and it is important to get off the road when you get to that point, but I'm with you, I LIKE to drive. On motorcycles, they call that an Iron-Butt Ride! :)

The intermountain west is a beautiful place, isn't it? It's where the phrase "purple mountain majesty" came from! I especially like that road around Glenwood Springs, CO.