Lets say you have some food you wish to save for an emergency. There will be the option to travel to the ice mountains and store your food there in a cave.
It will cost like 20% energy and you can only travel there once a day. you can carry like 10 carcasses on the trip to store it in the ice cave. Its expiration date will double there. When the food stored there is soon to expire you would get i message saying: "(insert lion's name here) has remembered about the food he stored in the ice cave it must be soon to expire, better go retrieve it." It will also cost 20% energy to retrieved the food but you can also deposit some food while you're there.

edit:
Maybe, it could cost 100sb to "build/prepare" the cave for storage. It could last for one month maybe or you could pay 2GB to make it a permanent storage.

edit:
Clearing this, when food is taken out of storage it will revert back to original expiration days, example:

food has 2 days, you put in storage now it has 4 days: one day passes and you take it out it will have 2 days; or 3 days passes and you take it out, it has 1 day.

Tau's suggestions:

-Maybe it could be something like a storage branch but for extending the life of food?

100 SB for four spots. Another 100 for four more. Etc. etc.

-Maybe the extension could have a limit, like....3-5 days? But it only lasts while you have it in the storage? That way no one can fudge and give all their food 15 days, etc. (its actually what i had in mind somewhat, though i prefer expiration date doubling, that way food expiring tomorrow can only have 1 extra day x3 i cleared this up above)

For example:
You have a Carcass with only 2 days left.
You put it in storage, it now has 7 days.
You take it out in 5 days, it reverts to expiring the next day.

That way you can still feed it, but you can't just abuse it by switching food in and out so give it all more days.

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If the ice mountains bothers you guys then we can just say that its an unusually cold cave in an unknown location ;P