As
LizzyM stated, you should undertake more than just MCAT studying; obviously, you would include in your work/activities section that you worked for 70 hours a week, etc during the summer and the adcoms can see the situation you were in.
The purpose of the MCAT is, from what I understand, to act as an equalizer of sorts--an equalizer for one's intelligence. This is severely flawed, of course; however, a "standardized" test such as the MCAT is the best possible tool adcoms possess in the present to assess students' intellectual capacities across varying undergrads. You might argue that the MCAT is not a test of intelligence and a test of how well you take a test; I would agree. But there is
some correlation, particularly in the verbal section, as to one's ability to think critically. A poor test taker should still have the intelligence to score well on the MCAT relative to someone who just does not have the intellectual capacity.
The difference between the boards and MCAT is that everyone at that specific school recieve a relatively similar "potential" amount of time/conditions to study for the boards. Premeds come across from dozens of different backgrounds, from typical 4 year undergrads to people several years removed and in the workforce. This leads to an uncontrollable aspect for prep time/conditions, yet adcoms can potentially put forth an effort to minimize variances by considering the workload at the time of taking the MCAT. A person's performance on a standardized test can be improved with various factors, such as financial resources and time allotted to prepping. This severely lowers the "intelligence" factor of the test; unfortunately, the test is the best tool we have over GPA variances. To minimize the effects of these factors, prep time and the like
can be considered by some adcoms, not all. Again, that is just one small variable, and I would imagine worth +- 1 to 2 (extreme) points at most.
One example to illustrate that the MCAT is coachable and dependent on prep time: If I were a test prep instructor, I would teach students to approach problems from a different perspective. For example, one released test question asked for the acceleration of a block down an incline, with answer choices 0, 7, 11, 13 m/s^2. 99% of students would start plugging and chugging.
However, you can solve that problem by just knowing that the acceleration of a block down a slope with no extra external forces must have a maximum of 10 and a minimum of 0. Knowing that, you know that if the block slides down the incline, the only answer choice that could possibly be right is 7. I've stumbled across quite a number of these different perspectives/tricks and they really let you breeze through questions in a few seconds. Coaching is definitely a factor in one's score.
Take the MCAT when you feel you are ready; there is no point in trying to time when you are going to take the MCAT.