Ditto for what has been said here about sleeping -- accept no substitutes for sleep! As or more dangerous than drunk driving.
Let's put it this way... Cheap motel room maybe $40 - $60 -- includes bed, shower, coffee in the a.m., TV, etc. = rested & ready to go.
No sleep -- ditch, tree, another car, busload of nuns, etc. Still no sleep, adjustable but still uncomfortable bed, aches, pains, lots of bills, lots of " 'splainin' to do, Lucy." OR... pine box(-es), coffin is probably not real comfy, and pushing up daisies sounds like too much work, with lots 'o 'splainin' to do" but to a much higher authority.
Cost analysis is pretty easy on this.
Longest trip was 650+ solo highway miles at night. Bad music, bad radio, bad roads, bad tolls, bad coffee, bad mojo, bad idea. Never again. Also, once dozed off for three seconds (no poop, three whole seconds) on the way home one night & woke right up to the red lights behind me. Spent ten minutes explaining that yes, I was just tired, yes, the ONE beer was four hours ago, and yes, that really was my house 500 yards away. Deputy was only beiing careful, and I was kinda glad he was, but then I couldn't get to sleep for four more hours. Take a nap before you take a dirt nap.
Now for long drives I take plenty of fluids, but not too much caffiene. I get too jittery and need to see a man about a horse too often if I do. Good food helps -- edible snacks (not made out of too much plastic), fruit, and a sandwich or two. Coolers are great, even the small ones.
Beg, buy, or borrow an XM radio. Satellite radio is digital quality sound, no or at least very few dropouts as long as the antenna can see the satellites to the south. That means you can listen to any or all of about 130 channels with no fading in almost all of North America. Check out XM411.com for info., if you'd like. Not just for road trips, but what a difference!
AAA+ is great and using it once pays for it. OK maps, but really good info on road construction, vehicle laws from state to state, etc. Unless you do the GPS thing, and even if you do, I suggest a DeLorme Atlas & Gazeteer for the states you'll go through. About $16 - $20 per state, but they show very nearly every road in the state. They have much more detail than any other map except the USGS topographical maps, and many of those are very out of date. DeLorme also does CD maps. Check them out and you'll see. Very handy when the detour or need to get out of traffic thing happens.