How much time before retaking GMAT

I'm no expert here, but just so I know, what are your mock GMAT scores?
Have the previous two attempts (660 and 690) been inline with your mock test scores, or have you consistently scored above these scores in your mock CATs (the dip in your actual GMAT scores could be due to various factors - exam stress, silly mistakes, even bad test centre conditions)?
690 is definitely a pretty good score. But I won't launch into a harangue about GMAT scores acting only as gating criteria. I am assuming that you have your mind set on a 730+.

Now, if you have consistent scores of 720+ in simulated test conditions during your study period, then I would recommend that you book your test date as soon as possible (a month later possibly).I see that you have finished all your study material, but are you sure you have squeezed the juice out of every single question in your OG, prep material and mock tests? If not, then you have something to spend the next month on.

If yur actual GMAT scores are representative of your mock test performance, then a proper SWOT analysis of your GMAT study-and-test-taking-skills is in order.

Cheers!

Thanks Stacy.
I have already taken the practice tests from mba.com
I scored 740 and 720 in gmatprep1 and gmatprep2 respectively.
I found gmatprep2 a little difficult than gmatprep1.
Also,Since I had already taken them once during my preparation for GMAT1, i was familiar with a few problems and that must have inflated my scores.
Is there any way to rejudge myself by taking a test other than mentioned above.I am asking this because I dont want to mislead myself by taking it and getting high score and then setting higher expectations from real GMAT also.
Please help.
Thanks.