Hi Gem,
Many Test Takers spend 3 months (or more) of consistent study time before they hit their 'peak' scores, so since your studies have been inconsistent - and with long breaks 'in between' - then that would help to explain why you have not scored higher yet.
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 2 CAT score results show that you essentially performed the same each time (about 630 +/- a few points). Thus, this 610 isn't that far off from your prior 650. You handle certain aspects of the GMAT consistently well, but you also make certain consistent mistakes. That having been said, if your general 'ability level' is around a 630, then raising a 630 to a 720+ would likely require at least another 2 months of consistent, guided study - and you would 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.
Many Test Takers who use a 'book heavy' study approach end up getting 'stuck' at a particular score level; from what you describe, your studies have been book heavy, so it's possible that you have gotten stuck too. Even the best books are limited in what they can teach you; they also can't force you to approach questions in a certain way and their explanations are often one-sided. This is meant to say that you might need to invest in, and train with, some new, non-book materials before you can get to the point that you are consistently scoring in the 700s.
In your prior posts, you did not appear to be facing any immediate deadlines, so you don't have to 'rush in' to take the Official GMAT in December. You might want to consider pushing back your Test Date and giving yourself more time to learn the proper Quant and Verbal Tactics. If you could follow the general study routine you've described for the next 2 months while working with some new study materials, then I bet that you could score significantly higher.
1) Do you have the flexibility to push back your Test Date to the end of January or early February?
GMAT assassins aren't born, they're made,
Rich