Hi Panavee,
If your goal (when taking a CAT) is to receive a realistic score assessment of your abilities, then you have to take each CAT in a realistic fashion - including taking the ENTIRE CAT (with the Essay and IR sections), away from your home, at the same time of day as your Official GMAT, etc. This also means that you MUST take a 'new' CAT each time, otherwise you will almost certainly see questions that you have already faced - and THAT is not realistic (the result of seeing those 'repeat' questions is almost always an 'inflated', unrealistic score).
If you're looking for general practice, then you can certainly take a CAT over-and-over, but you have to be willing to ignore the score results (since they will not be accurate).
Beyond the 4 GMAC CATs, there are plenty of reputable CATs that are 'close enough' to the real thing that they will provide you with a realistic score result.
1) Have you only used the GMAC CATs so far?
As a general rule, you should plan to take 1 FULL CAT per week (give or take). Since November 3rd is a Tuesday, I would suggest that you NOT take a CAT the weekend that immediately precedes your Test Date. You could take your last CAT the weekend BEFORE that one though.
GMAT assassins aren't born, they're made,
Rich