Never had a problem with a Zippo, they just work! As for number of lights on a fill up, about a week for a pack-a-day smoker. A flint lasts about a month at that rate, maybe longer. As for waterproof, if you submerge it for long, it will not work, the water will get into the packing and soak it enough that the fuel is useless. I carry a Scripto butane for stove and fire lighting. Strike anywhere matches in an old, old matchsafe and a Swedish Firesteel. Never failed to have a fire, if I needed one. One way or another! As for the butane at altitude, used it to light a stove at over 14,000 ft, worked fine. Cold can be a problem, but if it is in your pocket, it stays warm enough. The beauty of the butane, if it gets wet, let it dry and it will work again. Cheers!