I think they are fine for quite a long time not sure how long though. When you think about it a broody hen can take a while to get her clutch ready to start incubating and surely nature has a way of keeping them from going bad before she starts. let your nose be the judge and crack in a saucer or similar before using. Our dog gets any we find in a secret clutch and don't know how long they've been out but so far none have been bad. Usually I keep in a bowl on the counter for a week, then they go in the fridge until I find somebody to give the too and make more space.