When I was younger I would drive to Las Vegas leaving here at 6am (tell mom and dad had to go to work) arrive in Viva Las Vegas! at 9:30 or 10am (driving fast, 450 miles) Um, do stuff until about 3pm and head home. Home by 7 and complaining about the Traffic from work!
My sisters and I drove pretty straight through from So Calif. Through Nevada, all the way to Brian Head Utah to ski (7 hrs)
I easily make the 6 hour drive 10 freeway Southern Calif. To Mesa Arizona, straight shot. I have done that stayed 2 hours, and doubled back, home by 8pm. (left 4am, arrive Mesa 10:30 or 11am. stay til 1 or 2pm, home by 8 or 9pm. All in a day.
By the way, never leave So Calif. at 4 am and arrive in Blythe, Ca (before the Arizona border) at 7am. That Kentucky Fried Chicken only teases you. It does not open til 10 am!