'66
Time and materials for the changes, including the takedown and repackaging. 'Course, this part I itemize on the final bill.
In the end, the customer is left with a building with greater value as a result of my work, whether I got paid for it or not. The bid (contract), verbal or written, is set, but the changes can be simple T&M or flat rate, . . . the important thing is not to loose track of them.