Hi Mervyn,
I trust Engineer’s wisdom so hope you’ll have a productive chat :wink-wink You’re right most people, myself included would prefer last referrer.
As Engineer pointed out with session tracking you’ve only really got one shot at converting the user and that needs to happen straight away (unless maybe he downloads). With cookies there is tracking information stored on the player’s computer and depending on the cookie duration the affiliate will still get credit for weeks or months after. In other days common values for duration are 30, 60, 90, or even 365 days.