I was told to use Dry Ice in them and they will last longer.
We spent about $30 on dry ice and wrapped them up layered as shown. It only lasted two days and just vaporised.
Use block ice in them. Keep the icecream containers and freeze them. Ours lasted 7 days with block ice in a HOT summer and very little water in the bottom. The are worth every cent we paid!
We were told to use the ice gel packs to cure the esky before you go away. Get it cold before you go and then put the ice in. The ice will last much much longer. Don't take the gel packs away with you. They absorb every smell and juices in the esky. Use them to cure your esky before you go.
It really works!
Any man, in the right situation, is capable of murder. But not any man is capable of being a good camper. So, murder and camping are not as similar as you might think.