You should read the books. It kinda hints as to why Vader doesn't just dispose of Palpatine. Remember, Vader is stronger in the force than the emperor. If I remember correctly, in one of the books, it hints that when Vader was injured, Palpatine put him in that suit. It has a respirator in it. Hence the breathing. And in a thought, the emperor can stop the machine. And Vader dies. If he wanted him dead, he has to do it when Palpatine least expects it. That way he won't have the time to think about it. And he is always expecting it.
Just so you know. Yes, I have most of the books. Nearly all of them from Del-Ray books. And yes, I have read most of them. Call me a geek if you want.
But they are pretty good books. A lot of good story line, and back story that helps explain some of the movies. Hope it clears it up some.