It's certainly very close to be a "rule". Have you ever heard of the concept "Art from Adversity" ? This idea says that people give their best when they are challenged by others and their environment. They day they "get there" and make it big, they become lazy and stop fighting and end up having their way no matter what crap they produce.
PS: As for Samuel Jackson, I don't really like the guy because he's just too much into money and wants to put his face on every movie possible out there, but he can play very well some types of characters, just like the one you mentioned in Pulp Fiction. He's great when shouting and swearing. It was just very poor casting to put S. Jackson as a Jedi Master because he certainly lacks all the composure to pass as a calm, wise Jedi.
I think it's clear he wants numbers from someone who's actually studied this rather than going off intuition and anecdotes. That's because we have numerous cases where study has shown intuition is wrong, and going by what is memorable can give vastly different results than going by what is common.
Usually what people did in the past is a very poor indication of what they'll do in the future. Numerous examples in the art industry of people being very good at one point of their lives and then doing shit forever after.