Zippos don't go out until you close the lid and suffocate the flame. Unlike the Bic style, you don't have to hold down a safety to keep the flame burning. Once you light the wick, it keeps feeding fuel until the flame goes out. (which is technically slightly after the lid closes, so there will be the smell of unburnt fuel if you reopen it). However, unlike a Bic, the fuel is actually absorbed into cotton balls inside the lighter, so it's less of an explosion hazard.
The technology isn't that far-fetched for the average fantasy-medieval setting, where wick-based oil lanterns and flint-and-steel are both considered common items. The Zippo is just a thumbwheel of metal that strikes a piece of flint, creating a spark that ignites the fuel-soaked wick. The machining for the thumbwheel might be the toughest part, though if you allow gunslingers, you're probably fine.
You'll get a week to ten days out of the fuel, whether you use it or not, thanks to the fact that they're not airtight and the fuel evaporates.
I don't know Pathfinder well enough to give you game stats, though. :/
