The fuel evaporates pretty fast.
Not if you slip a "ranger" rubber band over the opening. (I cut my bands from a bicycle tube.) I've run experiments with my three Zippos several times, and one filling of fuel will last for about ten weeks. For the experiments, I've fired the Zippo up twice daily for about seven to ten seconds, about what it would take to light a handful of tinder for my campfire. As I said, ten weeks and it still burns.
Obviously leaving the "ranger" band on the Zippo would be inconvenient for a smoker who knocks off a pack or two of cigarettes a day .... but I don't smoke.
Also a major advantage of a Zippo is I don't have to keep holding down a button for it to stay burning, and it is windproof, too. I also carry a couple 1/8 oz. cleaned Tabasco bottle filled with fuel, in my daypack.
I would not be without my filled-with-fuel Zippo when I am going out in the boonies, etc.
L.W.
