------------------------------------ When a chicken lays an egg, the shell is sealed by a coating similar to cooking oil.
During the cleaning and candling process this coating gets removed thus removing the natural protection of the shell.
Common trick for sailors, including myself, is to buy eggs from the farm if possible, then coat shells with cooking oil and store onboard in a cool place, turning eggs end for end every 2-3 days.
Have kept eggs this way for about 6 weeks with no problems.
Probably could have kept them longer, but the cruise was over.
Lew