How long can eggs be left out?
If the eggs have never been refrigerated, they can be left out in a cool place for up to a week. If the eggs have been refrigerated and you take them out of the fridge, then no longer than a day. There's also a test you can do to check if an egg is still good. Fill a bowl with water. If the egg floats, it's past its prime. If the egg sits on the bottom of the bowl, it's still good.
Do you mean until they hatch into chickens?
American eggs are 'washed', which means that the outer, natural coating has been removed and they really should be refrigerated, though as Amanda says, you can do it for a bit. European eggs, however, are not subjected to the same treatment and can be stored at room temp.
When I was on a three-week wilderness trip a few years ago, the outfitter, a firm with a great reputation, packed our eggs in a box rather than a cooler.
Yes Greenstuff. I have been on a 3 week and several one week wilderness trips, also packed by reputable companies and the eggs are kept in a cool box. Not cooler. Never a problem.