Small portable gadgets using LiPoly batteries (which I assume the Tesla is using) can be left for months or years without charging, and then nursed back to life. If sufficient charge is left in them, and the circuitry is smart enough to recognise that the battery's about to die, the time before complete discharge could be extended to a much larger period of time.
The solution could even be a one-time use fuse, isolating the battery completely. Given the option, I think most owners would rather have to replace a fuse than a $40k battery.