I generally carry a Zippo as part of my firekit. Since I do not smoke I tend to forget about this lighter in my vest. It used to always be dry of fuel when I wanted it, so I took to filling it and wrapping it in 3 or 4 layers of Saran wrap held in place with rubber bands....not convienient to get to, but my experience was that it usually had fuel when I did want it.
Of course, I never really knew how long it kept fuel, so last time I fueled it I included a tag with the date.
Today I needed to melt some nylon tape for a repair I was doing (at work, so did not want to use a strike-anywhere <img src="/images/graemlins/shocked.gif" alt="" />), pulled out the wrapped Zippo and it fired right up.
It was almost dry though. I carry a Tabasco bottle of fuel and it took 3/4th of that to resaturate the cotton.
So it looks like about 7 months carried in my vest pocket wrapped in 4 layers of Saran.