first, i'd like to brag that out of 27 eggs set three weeks and a day ago, 24 have hatched. this is from the first use of a pre-set gfq model 1588 hova bator. they've taken all of the guess work out of this incubator. all you have to do is put it in the right location, fill one water trough when needed until day 18, when higher humidity is required, and sit back and watch the eggs through the large glass windows on the top. an excellent product. now that i'm off my soap-box, i'd like to know why eggs more than 7 days old should not be put in the incubator. my reason for questioning this is that when a wild bird, say a guinea, makes a nest, it may lay an egg a day until more than a dozen eggs are laid and then she begins to set. i've seen guinea nests with almost twice that many eggs, and to my knowledge, the bird can only lay one egg a day, max. so when the hen starts setting, the earliest eggs laid can be over two weeks old. certainly they're not kept in the ideal environment until the bird starts setting, yet most of these eggs will hatch. so, i guess my question is, if eggs older than seven days are often hatched by natural incubation, why is it not possible to set older eggs in an incubator? thanks, anybody who has an opinion on this.