I do what Bannock does and feel that I can use them whenever in spring and fall if temps have been cool or by day three in summer. I try to make sure the eggs are kept sfae and suurround the container with cardboard as well as surround that with stiff things near the top of the pack. I also place the cardboard egg package in a big zip lock just in case an egg breaks. Having a broken egg all over the inside of a pack for 7 days in July gets pretty stinky-Trust me I know.