Hello. So I was in your shoes a couple of years ago. The answer really depends on your abilities, how much time you actually have (ie, do you work?), and what the requisites in your college look like. For example, mine allowed me to take Chem 2 with OChem 1, while other colleges require that you take Chem 2 before OChem 1. I was also allowed to take Biochem with OChem 2, which I am very happy about.
The fastest timeline I can come up with for you is about 1.5 year before MCAT, but that's really pushing it for no real gain in time since you still won't be able to apply. Two years sound reasonable, if you've taken all your pre-pre-requisites (Algebra/Trig for Physics come to mind). Three years seem quite leisurely, but very reasonable if you're working or know you can't handle 2-3 science classes per semester. The best timeline is always whatever will get you the most As. Good luck!