I think most people do well with 2-3 months of studying prior to the exam (obviously others have their own style). From what I've gathered from personal experience and from peers, it's really hard to remember things if you learn them too far in advance, even with regular review (which can become frustrating as you see yourself continually forgetting more and more and spending more and more time just reviewing instead of plowing ahead). In the last few months as you are learning the material you will also be doing practice tests to apply your knowledge, and that helps everything stick, if even for a little while. Good luck!!!