Honestly, holding up Star Wars as an example is an exercise in futility. George didn't even write the Star Wars novel - one of the worst-kept secrets in SF-dom is the knowledge that Alan Dean Foster was the ghostwriter for the novels. Luke and Leia were not supposed to be brother and sister until everyone noted how much more chemistry Carrie and Harrison had on screen than Carrie and Mark - hence, the convenient "She's your sister", so there wasn't any "love triangle" between Luke/Leia/Han after the 2nd movie. (And the prequels weren't even a dream until well after the first trilogy - obviously or there wouldn't have been so many continuity flaws between 1-3 and the original 1-3. *sigh*) Marvel went nuts trying to do the comic series because George wouldn't tell them what was going to happen in the upcoming movies, it was "Do what you want but George gets to veto anything for any reason." Lots of story lines got killed at Marvel because they got too close to stuff George did or considered doing in the later movies. The extended universe novels were under George's direct approval (unlike the Star Trek novels, which are most pointedly "not canon" according to Paramount).
Star Wars is actually a great example of watching as story shift over time but the movies and novels did a great job adapting and ensuring plot points changed in a reasonable manner to account for what came before.
