When you're deep into a multi-day mission, the most important question isn't just "Is it cold?" — it's "How much longer will it stay that way?"
Long-term ICEY TEK user and researcher Ian H. has been tracking the performance of our gel ice bricks for years. Through consistent field testing, he has developed a reliable method for predicting how many days of cooling you can expect based on the volume of frozen material you pack.
The 40/30/20 rule
Ian's research shows a direct correlation between the percentage of the cooler's volume filled with bricks and the number of days the contents remain food-safe. Assuming you pre-chill your ICEY TEK and keep it out of the sun, here is the formula for a 3 to 8 day trip:
40% gel bricks: Expect 7 to 8 days of cooling.
30% gel bricks: Expect 5 to 6 days of cooling.
20% gel bricks: Expect 3 to 4 days of cooling.
"The reason for the different percentages was to allow for different size boxes to have sufficient space," Ian explains. While 40% offers maximum longevity, a 20% ratio allows for more food and drink utility on shorter weekend trips. If you want to understand the broader science behind why ice volume and placement affect retention the way they do, Maximise the Chill: The Science of Ice Retention covers it in detail.
Ian's core principles for long-range cooling
To achieve these results, the how is just as important as the how much. Ian follows a strict protocol for every trip:
Foundation first: "Always cover the bottom of the box with bricks first, the rest around the walls and gaps," Ian advises.
The bottom-up logic: Ian noted that even when the upper part of the box passes 5°C, "the bricks in the bottom were still pretty much frozen." This means drinks or high-risk foods kept at the bottom remain very cold, extending the usable life of the cooler.
Pre-chill everything: Ian precools the box and packs only chilled food to ensure the bricks aren't fighting internal heat from the start.
Eliminate hot spots: "Never put the box in the sun," Ian warns. He also uses frozen bottles to "supplement the bricks and fill smaller spaces," effectively turning dead air into extra cooling power.
Scaling for your mission
Whether you are using a Pro Series 50L Hard Cooler for a 4-day run or a Core Long 260L Hard Cooler for a week-long commercial haul, these percentages serve as your roadmap. While weather and opening frequency cause variations, Ian's figures are built on actual usage for general food in real-world Australian conditions.
"Bricks in the bottom were still pretty much frozen... so this would increase the usable days if there wasn't much meat etc left in the box." — Ian H.
For guidance on keeping food safe once the temperature starts to climb toward the end of a long trip, see Packing Meat and Dairy Safely in a Cooler.