The experts will tell you 10 days or less is the best. Many will won't go past a week. It's pretty much agreed that past 2 weeks significantly lowers the hatch rate.From what I've heard it's 10 days. Put them in sterile egg cartons and leave in a cool place (no, not the fridge ), fat end up.
Most people believe in turning them while storing just as you would during incubation. If you have them in an egg carton, you tilt the egg carton 3xs a day. Some people use the auto turners for the incubators and just have them on a table or counter.I think it is better to move the eggs around a little when you are storing them. I wouldn't leave them just sitting in an egg carton.