To counter the evaporation problem there are little brass fuel tanks for Zippo and its clones. You have to remove about two thirds of the cotton wadding and the felt pad to accomodate the tank but this works great and a freshly filled zippo will last a lot longer now.
Beyond this I've even further resolved the evap prob by cutting about one inch of bicycle inner tube and fit this around the lighter and this performs extremely well in conjunction with the tank. Just roll down the innertube enough to open the lighter and flick as usual. I basicaly works much like an O-ring. I lit my zippo on the first attempt after not being used for 4 months this way.
Give it a try !
Pharaoh.