From my understanding, some model S ship with more batteries than required and the additional capacity can be unlocked via software upgrade at a later time. If you see degradation and decide to upgrade years after buying your car, will the unused cells degrade too? I reserved the M3 and trying to keep it under 50K. Waiting on the battery upgrade will free up room in my budget to get things that aren't upgradable later (nicer seats, panoramic roof, etc) -- but I'm concerned that the value won't be there considering a) you pay more for upgrades after purchase and b) you may not be getting the most of cells that are potentially years old. Anyone with knowledge of these types of batteries, or experience with tesla battery upgrades able to comment?