The ideal conditions to store eggs to hatch are in temperatures around 55 degrees F (13 C) and in high humidity (80% has been suggested). The eggs should be turned daily, different ways to do that. Store them away from bright sunshine (can heat them up) and keep them away from air vents that can blow air on them. Eggs stores in these conditions can stay viable for over two weeks.
Very few of us have conditions close to this. I don't. I store my eggs in a spare bedroom at house temperature in the 70's F (under 25 C). The humidity is usually pretty low due to the heating or AC. I turn them by hand three times a day. I used to take the turner out of the incubator and use it to turn them but the wife got a house dog so I have to keep the eggs in a dresser drawer away from it. Can't use the turner anymore. I can store mine for a week this way and still get good hatches.
Hatchability does not all of a sudden stop for all eggs. The longer you store them the less likely they are to hatch. I always stop storing them by one week because by then I have all I need and I get good hatches. Many people report having good hatches storing them in conditions as bad as mine and still get good hatches after 2 weeks of storage. So I'd store them until you have your 6 eggs and set them, expecting the fresher ones to hatch and probably getting chicks from the older eggs. Your cellar sounds like a good choice.
Good point. With one frizzle rooster, one non-frizzle rooster, and one non-frizzle hen you would need to separate the hen from the frizzle rooster for three to four weeks, otherwise there is a chance some of the chicks will be frizzle.
