Mister Freeze AC Revitalizer does not expire. You can keep the product as long as you want and until you are ready to use it again as long as you store the unit correctly in a cool environment that is not too hot and the battery tabs have not been pulled. Extreme temperatures in storage will increase pressure in the can and can be dangerous since the contents are under pressure. Once battery tabs have been pulled, the battery will start to degrade.
Note: Mister Freeze Digital AccuFill® Trigger display and temperature sensor do contain batteries that degrade over time.