I think Jack McCornack has done it. Maybe more than once...
500 miles a day is a good round number. 60mph is still a good number for average speed; if you have to make a few fuel stops, that's a mile a minute. 500 minutes, that's about 8-1/2 hours behind the wheel. Most people can do 12-16 hours the first day, but the second, third, and fourth days get exponentially miserable. 8-9 hours, you can start Day 2 without being wasted.
From my experience at long-distance motorcycle touring and long car trips, I offer the following:
1) noise can wear you out. Bring some *good* ear plugs. Muffs are even better, but illegal in some states. (in Arkansas, for example... for "safety", though there are no restrictions on deaf people driving...)
2) people might stare at you for wearing a helmet in a car, but in an open car it does a fine job of protecting your eyes from grit and rocks, and your ears from windburn.
3) on a bike or a sporty car, you're basically locked into one position. It's not like you can shift around on a nice bench seat. After a while you'll find pressure points that hurt. I used to bring a cheap thin pillow with me. Nowadays I'd use one of those shaped Sorbothane wheelchair pads. No, they won't prevent soreness... but they'll move the pressure points slightly, and that's often enough to let one sore spot recover while the other is holding you up.
4) stop at *every* rest area, whether you need to or not. Just get out of the car, walk to the water fountain, and get back in the car if you don't have any other business to deal with. You can do it in less than five minutes. Just being able to stand up and move around for a minute or two helps a lot.
5) boredom can be a big factor. I used sound-blocking ear buds inside my bike helmet; the helmet quieted the wind noise enough I could listen to audiobooks or music with my little MP3 player.
6) if you're not pressed for time, don't make it a race. Some people push to make as many miles as they can every day. The way I look at it, once you have to stop to sleep, pushing for miles starts looking silly. If you only drive 5 hours, fine. If you feel like rolling on for 10, go for it. There's no need to run exactly 8 hours.
7) and when you get miserable, STOP and get a motel. Conversely, if you wake up ready to go at 3AM, there's no need to sit in the room until 7 or 8AM.
people will probably see the car and your luggage and ask questions. Budget some time for that.
9) remaining seated for hours in hot weather, it's possible to get heat rash. Also, windburn.
10) if you have a specific destination, you only need to bring what you need *for the trip*. Extra clothing, etc., you can mail to your destination. And back. Don't carry anything you don't have to, particularly in an open car. If you have an urgent need for underwear or socks, Wal-Mart and K-Mart are everywhere. 3-packs of underwear can be had for $10; some bikers just throw the used ones away each night. Which sounds wasteful, but that's the price of one cup of coffee, some places.
11) if you're planning a specific route and stops, make motel reservations ahead of time. I got burned by that more than once, when there was some kind of ball game or convention in the area. For a large event it's not unusual for even small motels a hundred miles away to be booked up.
12) don't forget your phone charger. And don't forget to use it each night. And don't forget to put it back in the bag when you leave...
13) bring your medical insurance card, and a list of contact numbers, drug allergies, and the contact information for your primary care physician. *And* the contact information for someone who can make medical decisions on your behalf should it be necessary. Not just a wreck; my wife rolled in from a week-long trip once, very ill, and was on the operating table a few hours later. The degree of formality required for this sort of thing varies a lot by state; while you can use a lawyer for that, your local hospital's admission desk should be able to provide you with a boilerplate document you can fill out. Don't forget to leave a copy with your designee.
14) bring a ziplock bag for your wallet, watch, phone, etc. if it rains
15) rain gear is only slightly effective on a bike. When you're seated in a car (my old Spitfire had no top) it's worthless. Embrace the wet. You'll get blown dry quickly when it stops raining.
16) don't carry everything in your wallet. Split your cards and money between your wallet and one of those ID card holders that hangs around your neck.
17) if you take prescription medication, bring the bottles. There are actually some fairly nasty Federal laws about that. They're normally only enforced with regard to narcotics, but they apply to everything with a prescription. Bring what you need for the trip plus a few spare doses, leave the rest at home. If your trip bridges a refill date and your insurance carrier won't authorize an early refill, call your doctor and ask if he can give you some samples. Drug vendors drop off pounds of "sample size" drugs at doctors' offices; if you're on something common, chances are there are some samples around.
18) post your route here and any other appropriate forums; you can take the opportunity to meet some people you've only talked to on the 'net.
19) if you're touring, there's a lot more to see than just "Interstates and Cheap Motels of the United States." Upside: intermediate destinations. Downside: you need to shedule around check in/out times so you can leave your stuff at the motel. (and some places are nice enough to let you park your bags behind the counter outside of check times)
addendum: Iron Butt Association "Archive of Wisdom"
http://www.ironbutt.com/tech/aow.cfmA 7 is way closer to a bike than a normal car...