Reminds me of "lifetime free service" for Tivo on set top boxes. Occasionally they would let you transfer it to a newer box, but mostly if the box died, your lifetime service premium died with it too. It is lifetime of the hardware, not lifetime of you. One reason to do "month to month" if you plan to upgrade frequently. I have bought many Tivo lifetime service plans for different boxes over the years.
When Tesla offers FSD as a "pay as you go" type service instead of one time fee, then you can decide if you expect to keep your car long enough to buy it.
It makes sense to me that it would stay with the car if you sold it, and you would need to buy again for a new vehicle.
*BUT* it would be really nice if Tesla were willing to make exceptions for totaled vehicles if you replace it with the same model again. Seems like that would be "fair", but not an obligation.