Cookie duration is the amount of time a cookie remains in a user's browser before it expires. This is important for affiliate marketing because it determines how long a customer can be tracked from their initial click on an affiliate link to their final purchase. The longer the cookie duration, the more likely the affiliate will be credited with the sale. For example, if a customer clicks on an affiliate link and then makes a purchase within 30 days, the affiliate will be credited with the sale if the cookie duration is 30 days. If the cookie duration is shorter, say 7 days, the affiliate will not be credited with the sale if the customer makes a purchase more than 7 days after clicking the link. In order to maximize their sales, affiliates should look for programs with longer cookie durations. This way, they can be sure they will be credited with any sales made within a certain amount of time after a customer clicks the affiliate link.