I have seen many people claim that Zippo lighters are terrible for field carry because, as was stated, the fuel does evaporate over time. It seems like they never even consider carrying extra fuel, just as I am sure they do for any stove they use that is not wood fired, and carry batteries for electronic devices and flashlights, extra matches, and pretty much any other item that uses consumables.
Small bottles of lighter fuel are available, and they do not evaporate much, except under pretty extreme conditions. An Zippo makes (or has made under license) a very effective fuel canister similar to a cache tube. It, too, will evaporate over time, but carrying a couple of them, even if not checked on a regular schedule, will usually still have enough fuel to get a lighter going.
And if plans are carried out as they should be, Zippo lighters, and the fuel canisters, should be checked occasionally just as many other items in kits should be checked regularly. And certainly before any scheduled trip, Zippos and fuel canisters should be topped off before leaving.
Since I have been doing that, my Zippos have never failed me.
Just my opinion.