How long can they keep?

[havi]

I dont know if this is the right place to post this or not, but I have someone from craigslist that contacted me about buying some of my fertile green eggs. I only have one hen that lays this color and dont want to give her bad eggs. How long can I keep these eggs on the counter for them to be incubated?

 

[Goose and Fig]

I've had eggs sitting for about 2 weeks and every last one hatched. Some people say that you start losing fertility after a week though. Make sure you turn them too.