Everyone is different
I took the MCAT last August
Finished premed finals just before JUNE
Spent month of JUNE looking for a job and reading up on physiology, macromolecules, and about half of what there is to know about classical physics (subjects I never really had as an undergraduate). I also took my first half-length Kaplan test and performed miserably.
Took my first full length test (R-V) the first week of JULY and performed okay on the sciences and miserably in verbal.
Spent month of JULY sitting in on Kaplan classes (our teachers had been teaching for years and had scored 99% on the subjects they taught) and splitting my time more or less evenly between the three subject tests. I studied for roughly eight hours a day and more on days I took practice exams.
Spent first two weeks of AUGUST doing practice exams (AAMC I - R-VI) and reviewing (read "learning") unfamiliar material from the official AAMC MCAT syllabus.
Took one practice exam a day on the week and a half leading up to the exam. During that time, I also joked around with the kaplan kids (MCAT, GMAT, LSAT, and USMLE-step I & II students)... even went out to the bar the night before our friend left to go take his MCAT out of state.
I also checked out the building where I'd take my exam. Got a sense of how I could set my stuff up - how much space I'd have... after all, you're gonna be sitting there, writing for ten hours! I also worked out a time strategy... TIME STRATEGY, something few of my classmates thought much about.
The test itself was NOT BAD. I used my time strategy and finished each section with at least a few minutes to check my answers.
I think that unless you are a remarkable test taker, or your undergraduate college TRAINS you for the MCAT (mine sure as hell doesn't) then THIRTY HOURS A WEEK in the month or two leading up to the test should be a MINIMUM!
I am generally not a big studier. I can do just as well studying the night before an exam than studying an hour a day for it... HOWEVER, on the MCAT, there was a HUGE POSITIVE CORRELATION between the amount of time I put in and improvements in my score!
Your PRACTICE TEST SCORES should tell you where you stand and what needs work (the real practice ones... third party ones are garbage, esp in verbal).
Oh yeah, and I think the writing sample is scored by a five year old - I wasted a lot of time preparing for that. Should have picked up an astronomy textbook instead to prepare for that b* of a physics passage 🙂
GOOD LUCK!