Permafrost High Performance Coolers have extraordinary thermal properties through choice of manufacturing materials and features such as the Pressure Release Valve which allows for purging without opening the lid - thus mitigating loss of temperature.
To get the very best from your cooler for long term cold storage we recommend pre-chilling the cooler, to avoid using your pack-ice to make the initial reduction in temperature within the Permafrost Cooler. This is easiest achieved by freezing two water filled gallon milk cartons and leaving them in the cooler overnight, then remove at the time you pack your Permafrost Cooler for travel. A pre-chilled cooler can be expected to hold it's temperature below freezing for at least a week (up to 9 days in our field tests). Obviously, once opened or left open the thermal expectations may be compromised depending on the ambient temperature.
A large (45 or 75 quart) Cooler for adventure long storage, opened once a day to replenish a small (20 quart) size day use cooler gives the best of all use of the thermal capabilities of Permafrost Coolers.