Was wondering about that post.
I think this is where what we do is more of an art than a science. Each work is unique (to a large extent) and works differently than other systems. As we give it to someone to use, they find different ways to use it and ask us to change it. It continually goes around like that as we modify, they react to our modifications and the circle continues.
My contention is you should expect this. We are dealing with a very malleable thing with software and when a client/customer/user wants to mold it, we should be ready and happy to continue to evolve it. Don't be upset, they are paying you to meet their needs. By being glad to meet their needs, you stand out and prove yourself as their developer of choice.
Steve Jones