The general rule for eggs remaining reasonably viable after being laid is a max of 7 to 10 days. After 10 days the number of eggs that will grow keeps going down. You want to keep the eggs at a cool temp while waiting to set them...so think ideally basement-ish temps in the 50s or 60s with some humidity to keep the air cells from evaporating too quickly, but not too damp where condensation could get on the egg. Room temp is fine too if you don't have a cooler area, just keep the eggs from getting over 80 degrees-ish and from freezing while you are storing them before setting them, and NO refrigerator as once again condensation is an issue. You do NOT need the eggs to be warm when you collect them. They just cannot be frozen since the freezing causes cracking and possible condensation which introduces bacteria to the inside of the egg.
The eggs also need to be rotated side to side in their storage carton or turned a couple few times a day while being stored before setting in the bator. This keeps the yolk from sticking to the shell which tends to make the egg non-viable. Always store the eggs with the wide side up higher and the skinny side down so that the air cell will be at the top in proper position. Be sure to wash your hands before and after touching hatching eggs so that you don't introduce your hand coodies to the eggs, and so the oil on your hands doesn't gradually block the pores of the egg.
I recommend Gail Damerow's book "Hatching & Brooding Your Own Chicks". If you have never incubated before there is a lot to learn so that you will have good hatches and avoid common problems.
Good luck and have fun incubating!