If you used the extra time such that you shifted your intense study to the 4-6 weeks before the exam, and used the earlier time period that freed up to do some conceptual and general reading, then yeah, I can't for the life of me see how that could be a negative. So long as you aren't extending your intense study time and burning out before the exam, I don't think you would run much of a risk of being counter- or non-productive.
For that earlier study time you now have free, look for books that are more of a "general read" and somewhat entertaining, not a condensed set of tables and bullet-lists and pathway diagrams that need heavy memorization. Something like the Clinical Micro Made Ridiculously Simple, where you can read it like a book and things will stick with you. Or go through the lecture series at
www.pathguy.com where you will find notes that can be an interesting read on pretty much all of pathology, littered with the guy's thoughts on economics, politics, etc. that keep the reading somewhat entertaining. You'll forget a lot of the details, but if you remember more of the big picture and get a better grasp of things your conceptual framework into which you stuff details before the test will be more solid. Or if you have access to video or audio lectures that are more "passive learning" do those early to help get the big picture. You can always repeat certain lectures or topics again that were high-yield in important details closer to the exam.
Two things I want to point out... it seems that most people in this forum recommend a sort of "rote learning" strategy for the USMLE, relying heavily on short/medium term memory to stuff a lot of the details in before the exam. While I am sure that a healthy dose of heavy memorization and intense study before the exam will probably raise anyone's score, it isn't the only way to learn. So the first thing I want to point out is that true learning isn't done through memorization, and studies have proven that. Hopefully your first two years were true learning with long term retention and integration with other knowledge (I'm not so sure that mine was...). The details might fade with time, but the big picture is still there and will serve you well both for the exam and beyond. The second thing I want to point out is that even if you rely heavily on memorization, you should remember that repetition is the key. People here talk about "forgetting things you had already learned" if you study too soon before the exam. Well, sure, but that's one more time you've seen the information, and it will be that much easier to memorize and stick just a little longer the next time around.
