Yes, fresher the better. You can place 1 or 24 eggs in. I like to collect 5 before setting them, just to make sure I get enough babies that I don't need to buy a friend if only one hatches.
Try not to stagger the hatch too badly, within a day or two is fine, but a week or more can cause lockdown and hatching problems. For example, collect 5, then also place egg 6 and 7 in there. Mark them with the hatch date, 7/14 for example. So you would have 5 eggs marked 7/14, one with 7/15, one with 7/16. If you go for collecting another 5 and then set those as well, they'll be another week behind and things can go down hill.
You can also collect for 10 days, really the longest to retain viability. Some say 7 day. If your house has a/c and stays a constant temp, that increases the time you can collect. If your house has the windows thrown open and the temperature fluctuates a lot then you want to set them sooner rather than later.
Don't forget to turn the eggs you collect 3 times a day while waiting to set them. I did a staggered hatch with my ducks, I found one, and didn't think I'd find more, but I found two more. Then I received shipped eggs I had bought, and set them too. 4 different hatch dates over the span of 5 days. The 3 I found all hatched, just one from the shipped eggs. You wouldn't want to stagger more than that.
