Just had a look in my duck book (i know your's are hens eggs) and I think the info there is relevant for hens eggs to.
From: Storey's Guide to Raising Ducks. By Dave Holderread.
Length of storage.
Ordinarily, the shorter the storage period, the better the hatch. A few eggs that have been held 4 weeks or longer may hatch but for good results the general rule is not to keep eggs for more than 10 days before setting them.
The negative effect of long term storage periods on hatchability can be seen in the results obtained from a test involving several thousand eggs.
Length of Storage. Hatchability percentage
1-7 days 71
8-14 days 64
15-21 days 47
22-28 days 18
Setting eggs.
Start the incubator at least 48 - 72 hours ahead of time and make all necessary adjustments of temperature, humidity and ventilation before the eggs are set. People frequently put eggs in machines that are not properly regulated, thinking they can make fine adjustments after the eggs are in place. This practice is a serious mistake since one of the most crucial periods for the development of the embryo is the first 4 or 5 days of incubation.
End of book quote.
I personally have never used an incubator and have only used a broodie hen. When I've received eggs through the post I've removed them from their polystyrene packaging and put them into a normal cardboard egg box. I then let them get to room temperature and turn then once every 24 hours. I let them sit quietly for 48 hours before putting under the hen.
I hope this helps and best of luck with your hatching.
OL