Once the battery and drivetrain warranty runs out I would think it would be very risky for someone to buy a used Model S. There does not seem to be a way to just fix a battery pack, drive unit, or PEM if something goes wrong inside. One must get a new one (or hopefully a cheaper refurbished one) from Tesla. This seems like a huge expense that you are basically gambling will not happen if you buy an old Model S. Won't that cause extreme depreciation on the Model S as it nears the 8 year mark? I know people buy old out of warranty cars all the time. Difference is if something breaks you can just take it down to the local Midas and get it fixed or possibly even do it your self.