Second, WIP makes changes more costly. When you change your plans, any work that isn’t done has to be set aside. As time goes on, the decisions that went into that work become outdated and have to be redone. Code for incomplete increments is particularly expensive: either it increases the size and cost of maintaining your production codebase, or it’s stored in a separate branch where it becomes increasingly difficult to merge back into production. Metaphorically, WIP rusts away. It either has to be maintained, reworked, or thrown away, and that’s wasteful. Keep it to a minimum.
