The zeitgeist is ever-changing. If you try second guess what people want, you'll miss it.
One of my biggest disappointments is watching the trailer for the second Lord of the Rings film and having Gandalf in it. Why? He died in the first one, why give it away in the trailer just to try and sell 1000 more seats? It's daft.
My scripts are always heavily noted. If I can take a director to one side and say, "Do you mind if we try this?," a few days before, that's usually a better way of doing it then on the day.