The key to doing well on the MCAT is to do as many science problems (passage or stand alone) possible within a 3-5 month period. Use TPR, EK, or Khan as one of your primary resources to learn the content. But don't waste your time going over the same content in all three resources. Use the other two only as supplement for when you get questions wrong.
You should instead do is as many problems you can in one day - with a good review of each problem. If you are weak on a topic, then go and study it in the other two resources or seek a tutor. Usually the solutions to the problem will give you all the information you need to learn it.
The key here is to constantly test yourself - even if you are not 100% solid on every topic. There are educational research studies done on how testing yourself is the best way to learn.
A lot of students retake the exam simply because they did not do enough problems or practice their first time around. Don't save exams or problems till the last month. Finish all the AAMC question packs and exams a month or more before your exam date. I know that sounds crazy but you have to remember that this is not your average university exam where you can simply do all the old exams the professor gave the class or you found the last couple of days. You have to learn from your mistakes and change bad habits. This takes weeks if not months to do properly.
You are essentially taking 5-6 finals at once. Preparing should be a marathon, not a sprint.
