I have been looking and looking and I cannot find anywhere that says if crushed cooked egg shells spoil. Our chicks will be here in late April (this will be our first chickens) so I was thinking about getting a head start and prepping the egg shells from our store bought eggs until our chickens are old enough to produce(I just can't see wasting them). I just don't want to feed them something that could be spoiled. Please let me know the amount of time you store your shells, so I can get a rough idea. Thanks!