Handwaving away 15-25% of your adult life with "usually the worst bit" doesn't sit well with me, neither does the "merely" in "merely doubling your lifespan".

Handwaving away 15-25% of your adult life with "usually the worst bit" doesn't sit well with me, neither does the "merely" in "merely doubling your lifespan". Y'know, given that "multiplying it indefinitely" is not actually an available option, whereas not dying at 72 from lung problems from a lifetime of smoking after several years of being nearly housebound then almost chairbound is an available option.