Maybe I'm conditioned to this because I never need to stop for a bathroom break before the car runs out of fuel. It really bugs me when someone want's to go with me because I know they are going to need to stop much more often. Of course they're guzzling a 44oz soda while I sip water as needed.
I usually do my 5-6 hour drive with no stops, or one quick bio break, but I recently took it with 2 other people and this forced 3 stops on us. One of the stops was 20+ min. This turned what should have been a 5.5 hour drive into a 6.25 hour drive. Absolutely horrible.
I'm no fan of distance driving, but it's a lot better to get it done and over with rather than add 10-15% to the total time.
Also, Phoenix to Spokane? Wow. Hope you don't have to do that more than twice a year.
While money can't buy happiness, it certainly lets you choose your own form of misery.