With 200+ hour run-times being commonplace among ordinary battery-powered LED flashlights, there's not much point in messing with crank-powered lights. The extra mechanical complexity more than offsets any perceived advantage in not needing batteries. They aren't any more reliable than battery-powered lights - In fact, their plastic crank, gears, springs, dynamos, etc. make them considerably LESS reliable than ordinary flashlights. Under protracted use, most of them WILL fail - often, when you need them the most.
If you absolutely have to own a flashlight that doesn't need batteries, any of the better quality shake-lights would be a much better bet. (Note that quality is crucial - some of the cheap shake-lights are really "fake-lights", built with a non-rechargeable battery that eventually runs down.)