You've got the right idea wanting to reward loyalty, but you'll kill yourself by penalizing what you call "disloyalty"
If I send you 10 joins and never send you another click I should get paid my fair share of whatever those 10 joins bill, for the life of the member.
You're already at a disadvantage competing with per signup programs because most webmasters chase the quick buck, trying to "force" the webmaster to send more traffic is going to make it that much easier for the per signup programs to steal your webmasters.
Bonuses for volume and consistency are great ideas, but any program that wants to lower my payouts because I choose to do something else with my traffic will never get a click from me.
