Cookies are used to track referrals. And, of course, such cookies have their expiration date. Basically, a cookie's lifespan reflects how long the prospective buyer who clicks through your link might make you a profit through a given campaign. Each time your referral link is clicked, cookies are enables and last 90 days. Any sales made during those 90 day on the NS Retail site will be attributed to you. Each time a person reuses your link, the cookies' duration resets.