On the last picture we spent two weeks on a transition in the second act. Frame by frame, three versions, a genuine argument about it. Nobody who has watched the finished film has ever mentioned it.

The scene that actually fixed the film was cut in an afternoon, and only because we had run out of time to be precious about it. We took forty seconds off the front, started on the answer instead of the question, and the whole middle of the film stopped sagging.

This is not an argument for carelessness. The two weeks taught us the shape of the problem even though the solution turned out to be somewhere else entirely. But it is worth noticing which arguments you are having, and whether anybody outside the room could tell you had won one.