Hi jyii07,
Since you've been studying for so long, I completely understand why you would want to be 'done' with the GMAT. However, THAT is not actually your Goal though - scoring 680+ is your Goal (and you should not lose sight of that).
GMAC has publicly stated that the Official Score that you earn on Test Day is within +/- 30 points of actual ability. Assuming a similar 'swing' in how your CATs function, your 4 CAT score results show that you essentially performed the same each time (about 580 +/- a few points). You handle certain aspects of the GMAT consistently well, but you also make certain consistent mistakes.
Since these Scores go back about 3.5 months, it's likely that you have gotten 'stuck' at this particular score level. Raising a 580 to the point that you can consistently score 680+ will likely require at least another 2 months of consistent, guided study - and you'll have to make significant improvements to how you handle BOTH the Quant and Verbal sections. Thankfully, the GMAT is a consistent, predictable Exam, so you CAN train to score at a higher level. There's no harm in taking your GMAT as scheduled, but you will almost certainly have to retake it again later - so you can save some money and aggravation by pushing back your current Test Date.
Before I can offer you any additional advice for your studies, it would help if you could provide a bit more information on how you've been studying and your goals:
Studies:
1) Over the last 4 months, how many hours have you typically study each week?
2) Over the course of ALL of your studies, what other study materials have you used (besides the books that you listed)?
3) Have you taken any of these 4 CATs before (at any point during your prior studies)?
Goals:
4) When are you planning to apply to Business School?
5) What Schools are you planning to apply to?
GMAT assassins aren't born, they're made,
Rich