I recommend doing AAMC tests along the way instead of saving them. Intersperse with TPR or EK or Kaplan or whatever you like.
Why? Because you need to identify your weaknesses in strategy as much as your content weaknesses. Strategy weaknesses take a lot longer to address, esp. in VR technique. VR techniques that work perfectly on non-AAMC tests often are not optimal for the real thing.
Also, you need the practice of getting used to the timing, endurance, etc.. Having more weeks to get this down will help build confidence. Figuring out that you have a major timing problem (for example) two weeks before the MCAT is a big stressor.
In addition, you need to know where you stand score-wise. Doing tests from multiple sources is not absolutely reliable, but it's a good indicator (i.e. if you are consistently scoring below 20 2 weeks before the MCAT, you might consider postponing).
There's a reason that all the test prep companies do full-length tests right from the start - it's because it's the best way to prepare.