I disagree with many of these people; go to bed early and leave around 1:30-2am. You will get a few hundred miles under your belt and when the sun rises it will rejuvenate you. Plus, when you get to your destination, it will be late, but not that late.
My advice is do not take your helmet off at gas stops, eat granola bars while you are driving, and mentally break down the ride into 300 mile increments. Finishing a BBG1500 was one of my most favorite accomplishments.
Also, the LDR undergarments are a must, and if you have, one of the wool seat covers.