How long do they stay fertile or good?

[Hegatha]

Once an egg is layed how long do you have to put it in the incubator or under a broody hen before its no good?

 

[emys]

They will keep at least week - more if kept in ideal conditions.

 

[Fritatta]

and i hear you can actually buy fertilized eggs in the refrigerated section of Trader Joe's and they will hatch.
refrigeration MAY lengthen the life, but Im not sure.

Mama hen usually lays several eggs, one a day. they do not start to develop until she sits and warms em up.