EACH action you request of affiliates to perform ought to have some "Explorer rank" value. Even signing up or logging in 5...10 times.

You can offer a badge for "threshold actions" reading 50 posts or adding 5 referral links to the Downline Builder. Even reward purchases for credits with "Explorer rank" points.

You have to remember that there are A LOT of owners and EACH is looking to squeeze as much out of affiliates as they can. So each has to make their sites, offers and rewards ATTRACTIVE and RELEVANT.