"'m getting really old, because I can remember the norm being: Starters go until they're getting their butts kicked. Then they're pulled."
That may be because the bull pens were no where as skilled as they are today. Its only smart when you can bring in a set up guy and then the closer when they both are throwing near 100 mph. And don't get me started as to WHY I think so many pitchers are throwing close to if not faster than 100 mph.