I have had fresh eggs last several days, even when it is very hot out.  Extra packing care and putting them on top of the cook kit or some other pack keeps them on your mind so you don't lean on them while portaging.  Salmonella is more rampant than you think...one book I read said it is endemic in the commercial chicken houses and they can't get rid of it.  That's why all the warnings about cooking eggs until they are not runny....as long as completely cooked, even if with Salmonella, they will not make you sick (no runny yolks allowed).  Putting them in their packing, in a cloth bag and dunking the bag routinely keeps them wet, and the evaporation lowers the temperature around them, especially when hung or set in the shade at camp.  IC