I have gathered eggs for 14 days and had very successfull hatches. When single mating I want enough eggs to make using the incubator worthwhile so I save for longer. 7 Days is optimum for hatchability. I store them on a shelf in my bedroom closet in egg cartons with a wedge under one end changing ends morning and night (if I remember!), it is about 50 - 55 deg. in there. I don't save anything for hatching that is dirty or lightbulb/oddly shaped.
Thanks! Before this, the day I set a broody up with eggs I'd gather all the day's eggs into flats instead of the basket and used gloves or tissues to move them. Then I was able to pick out the most regular looking eggs, usually in a variety of colors, to put 10 or 12 of them under the broody. I made no consideration of breeding ... my hatchery birds all run together ... just egg shell color, cleanliness, size, and "shape."
So this whole "gathering a clutch" thing, and caring about hatch rates, is new territory.
I think I'll keep the eggs in the storage room in the daylight basement where my egg fridge is so I'm sure to go in there multiple times a day so I can "turn" the eggs as you suggest. Obviously NOT in the fridge ... I'll keep the ones I want to hatch on a shelf. The cement walls and floor keep it pretty cool in that room ... its supposed to be a wine cellar. Ha!