Character Appearance
When an actor is evaluating a part, they try to keep track of how many scenes their character will appear. Will this script move them forward in the audiences mind or is it just a small part. If the character keeps coming back the audience will expect that actor to do something important. Why else would the writer keep bringing him back?
If the actor has a small part he should remain that way. Say he fills a seat in a café, you wouldn't want to keep seeing him in other locations. The same goes for writing a book. The character should fade into the woodwork if he doesn't move the story forward.
