I am currently in a studying "crunch" and take about three to five practice tests per day (skipping quant as I am absolutely focused on my verbal score as a literature Ph.D hopeful). I think a lot of the GRE (and I'm sure many would agree) is knowing the test itself--the format, the implication of questions, how the test "thinks" in terms of which answers are "best", etc. Practice tests are the best means by which I've become attune to what to expect on the GRE, not only as far as content but in terms of the underlying, often implied "question" the test questions ask. Look at any GRE prep book--the answers to practice questions aren't just listed, but explained. There is a system to this, I think everyone would agree, and learning the system is a good deal of the battle.
Also, good luck!