when the test draws closer, you should consider doing what i like to call the OPENERS DRILL.

the motivation here is the following question: "how can you prepare to solve problems time-efficiently?"

one excellent way is what i call the OPENERS DRILL. in this drill, you hammer through about 50-100 o.g. problems per hour, and just specify how you would START the problem.
that's right - you don't actually go all the way through the problem, you just start it and move on.
you see, more than half the battle against gmat math problems is won or lost right at the beginning of the problem: if you're off to a solid beginning, you'll probably do well on the problem, and, if you falter and take over a minute even to start the problem, you probably won't do so well.

this drill is pointless until the test is pretty close, because you have to have all your content down cold to do it. there are two advantages of using the openers drill in the last week before your test:
1) it provides BREADTH - i.e., if you slam through hundreds of openers, you'll touch on every conceivable subject area of gmat math within a few hours. if you're actually going through entire problems, the way you would midway through your preparation, you'll neglect entire areas.
2) it will point out, with brutal honesty, any weaknesses that still exist in your foundation of knowledge.

try it; you'll like it.