[GregK]

Cookie duration is how long a cookie stays fresh after it comes out of the oven....

Actually, every time a user clicks one of your links, they get a cookie saved, this is how your affiliate info is tracked. That cookie will usually stay for a while, so even if they click a link one day and go back to buy on another day, you will still get paid. Cookie duration is how long you have before that cookie goes away. A 90 day cookie will pay you if the affiliate spends money within 90 days after they click from your site, while a 30 day cookie gives you 30 days.

Pretty simple, but it is the core of our livelihood.