I too EDC a zippo lighter. I keep it in a nylon pouch made by zippo. I don't smoke, but my wife does so it gets used 5 to 10 times a week. I live in florida and I usually go a week and a half to two weeks between fills. I also overfill it and have repacked and fluffed the cotton batting inside the unit. I carry a spare flint under the felt "tongue" on the bottom.
I have about a dozen or so different zippos and can tell you from experience that some hold their fuel better than others. No rhyme or reason to it that I can see, although in my experience the brass cased ones fare better than the steel ones.

-Bill Liptak