As people have already discussed, voltage boosters for things like LED flashlights are already in wide use (usually called a "voltage regulator"). The tradeoff appears to be something like:
-- longer life at full rated voltage
-- when the battery dies, it dies suddenly and completely, no tapering down - one second it's on, the next second it is dead as a doornail
-- parasitic current drain drains batteries even when they're not in use
-- more expensive
They most definitely do NOT increase usable battery life by 8x.
-- longer life at full rated voltage
-- when the battery dies, it dies suddenly and completely, no tapering down - one second it's on, the next second it is dead as a doornail
-- parasitic current drain drains batteries even when they're not in use
-- more expensive
They most definitely do NOT increase usable battery life by 8x.