The first month is crucial. One cannot have all but a good way is probably to offer 5 TCredits to the first 10 new PSAs and first 10 new CSAs who achieve EA status within the month of signing up. That way, your expenditure will be limited to 100 TCredits a month and the statistics will separate the serious affiliates and those who sign up for the sake of signing up.
The TCredits will allow them to try out Tripleclicks and who knows?