What looks absolutely fabulous in rehearsal can fall flat in front of an audience. The audience dictates what you do or don't change.
I have to work really hard eight shows a week to get a nice check as an...
You do have to change things as warfare changes.
You can be the best actor in the world but if you don't have that one lucky moment it kind of doesn't matter. There are a lot of amazing actors who will never get the chance to prove themselves because they won't have that one lucky moment.