That is a good amount of time for planning ahead. You can signup for test date at any time - it depends on when that specific testing center has availability. So you should check out the test center link in the article below. You can see their schedule and how far that test center is already booked for.http://www.gmatpill.com/gmat-prep-about ... est-dates/
Our advice is to go ahead and schedule it now - it mentally commits you to a study schedule. Otherwise, it's very easy to get distracted between now and then. Typically between 1-2 months time before December is a good enough attention span time window for you to focus on one thing without being sidetracked. Aim to schedule it around now (since it's 2 months before December) so you can mentally commit yourself and work towards breaking your barrier high score.
Hope that helps!
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Zeke Lee, GMAT Pill Study Method (Study Less. Score More.)
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