I believe I have stumbled upon the very definition of churn:

The Story

For a certain project of mine, I originally implemented the system to support many “legal letters per case”.

Fast forward a month later, where we are told by business to only support one letter per case. After questioning them explicitly and incessantly about “are you sure you’ll only ever send one letter per case?!”, and getting the answer “We’ll only ever ever send one”. We did the work to make the system less flexible and support only one letter per case.

Fast forward another month later, where we are told by business that we want to keep track of multiple letters per case.

The lesson: Specify Behavior, not Implementation to programmers

And this is exactly what happens when your clients specify implementation instead of behavior: you have programmers/consultants make and remake expensive changes. If you had specified behavior, your consultant might have understood the scenario (as I did here), made the correct choice and avoided expensive churn.