That's always an ongoing issue on similar sites that give us an affiliate program with just an id name or an id number, and do not have an affiliate link instead. As if I like a site, I like to place it someplace on my sites or on other sites and if I do not have a link to get credit for them, then they just sign up and wouldn't even know who sent them.
As far as cookies are concerned, already thought all about that as well. On some affiliate sites a cookie is placed on their computer and it may be there for a few months, or a few years who knows. However, those of us who know computers usually every so often DELETE those cookies don't we? At least I do, I can easily clear them out and get rid of any junk such as any viruses by doing virus scans and I also delete cookies in case someplace watches how often I go there.