Considering how long you have been in this business, I am sure you know that there is always space for negotiation. If you have been scammed by your partners I would would generally ditch them in the first place. Of course this can hurt though if you have a large player base with a particular operator.
If you know how much your players are worth and the affiliate program knows you a bit as well, you will find programs that pay a fixed monthly fee. However, this is usually combined with rev share or CPA.