Not a stupid question at all - quite the opposite, really, especially when you are looking at the investment of purchasing eggs and going to the expense of shipping.
There are few different opinions you'll get on this - but for me, personally, I prefer to set eggs that are 1 week or less old when at all possible. Some folks have decent luck going up to 2 weeks. Keep in mind, too, that a lot of other factors come into play here such as how the eggs have been stored pre-shipping, how they were packaged, how they were handled in shipping, etc --all factors which can greatly reduce the likelihood of success if done incorrectly.