You can optimize it based on your exact application deadlines,there are 2 approaches: either you want to do it really early and keep giving the test repeatedly, if you are willing to spend the money and energy, that is, till you get your desired score. It may happen that you are really good the first time and so then GMAT is out of your way and you focus on other aspects of the application. Other approach is to decide, no matter what the score is, you are giving it only once and then give it just before the deadline and apply with whatever score you get, this way you are giving yourself more time starting today as for most schools R1 deadline is in sept. For example my gmat is in first week of sept, I am applying to only 3 part-time programs in bay area for fall 2012. The R1 deadlines for these are in november. So, I may want to give the gmat again if my score is not to the mark. But then it will conflict with the preparation of essays, which are a lot if you apply to 3 schools.
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