My experience with myself and hundreds of students over the years has been that cramming is essentially worthless, so I usually recommend that people relax during the week before the exam. Look at a marathon runner's training schedule - they aren't running marathons every day up until the actual race. They do a big workout about a week before, then take short jogs and walks during the week leading up to the main event.

So, I'd say to take a final practice exam about a week before the real GMAT under conditions that simulate the actual exam as closely as possible (do the essays, do the test straight through, etc.). Make sure you have your timing down. After going over the exam, see if there are a couple of main areas you want to do a final review of. Make sure it's something that you have a pretty good chance of seeing on test day - so, don't kill yourself over really tough probability problems, for example.

Then, it's time to relax! I don't advocate studying in the two or three days before the exam. Go out with friends, relax, get a lot of sleep, etc. so that you'll be on your game for the real GMAT. Like I said above, cramming doesn't really help - it usually just works people up into nervous messes!