I would start studying about a year before you take the MCAT. Studying now is kind of overkill. Focus on your premed classes first and do well in them. You can start studying when you finished all the perquisites (chem, physics, bio, organic chem.)
MCAT is more like a review of what you have learned in your premed classes. You don't actually need to know as much as you learned in your classes to succeed.
Of course studying early is better, but some people don't retain information for very long. I took the MCAT a year ago, and I honestly don't remember much of the stuff I studied on my MCAT. If I go back and study again, however, I'm going to be able to pick it up much quicker since I've already been exposed.
Also, MCAT is really testing on your ability to critically analyze passages more than retaining information from books. I know people who don't even study for the MCAT and still do extremely well. If you do a lot of research, it could help you a lot because you're exposed to critical analysis rather than rote memorization.