Here at Lovefilm we have built our affiliate program on promoting a 2 week trial and paying our affiliates £12-17 (volume pyramid) for every person they drive to our service. Our affiliates are told not to promote offers not on the network, such as the longer trials we use to win customers back or premia included promotions (wine, cinema tickets).
I am looking at allowing some affiliates to promote special offers such as a longer trial and cinema ticket giveaway, but this moves some of the affiliate commission budget into the offer instead. Affiliates have a choice - promote the normal offer and take the money, or try the different offer on a lower CPA but hope conversion is better (as it should be).
What do affiliate prefer though - a higher CPA with less risk or the gamble of 3 times as much (or less) money in the bank if the special offer works?