Every once in a while affiliates post (in blog, forum, or other social media channel) about merchants lowering the commission rates in their affiliate programs. History also testifies that this happens not only with smaller brands, but larger online merchants were caught doing this as well. Some justify commission drops by inaccurate initial calculation of the default commission level, others by financial constraints, but no reason will ever be good enough reason in the eyes of the affiliates.
You want to make your calculations right at the very outset. Lowering the commission rate (permanently or even temporarily) at any time during the life of your affiliate program is a grave mistake. It can easily bury your reputation, and your affiliate program. Put yourself into your affiliates’ shoes and you will understand why.
Respect your affiliates, and let your actions mirror this respect. You can go up, but never, never, never go down on that commission rate.