Now a few weeks I'd believe. They're not really made for long term storage while fueled... not exactly air tight either. Seriously... for a smoker they are wonderful lighters... but for an emergency, long-term storage type of fire making tool... there are much better designs... You can buy 40 bics for the cost of a good zippo... and they'll keep for at least a year... perhaps longer if you store them right. I know here in the georgia heat they run dry if stored in your car sometimes... not all the time... but sometimes. I bought a vacuum sealer a year ago and you can use one large bag and make multiple smaller ones... I will seal a bic in that thing and if the seal takes... I haven't had one die in storage on me... just make sure to put some sort of wedge under the gas pedal when you seal it... otherwise the bag might push the button and all of your fuel will slowly leak out and possibly pop that baggy. Vacuum bags are also how I store tender and cotton balls and such.