The thing is, although GL and Lucasfilm says that SW was always visualized as 4, later 3, later 2 trilogies, GL really only had "Star Wars" in mind as a single movie, period. There was no backstory and no sequel. After the movie was proved to be succesful, he came up with a backstory for episodes 5 and 6, calling Star Wars episode 4. He was quoted as saying that he would not produce the prequels nor the sequels, but eventually he changed his mind and came up with the prequels. It is MORE than obvious for all of us that he made the prequels up as he needed to. So he basically writes just as much as he needs to, and later lie, saying it's a whole part of a planned series. I mean, check out the novelizations, check out the original scripts, the deleted scenes, he had NO idea what was going to happen on the following movies (quoting Mark Hammil as he found out that Luke was Leia's sister: "Oh come on, George! You came up with that on the plane trip over here, didn't you?!"). Also, notice how GL has given contradictory answers when asked if Anakin disapear when he died...

Is there anything wrong with that, with coming up with the story as you go along with it? Hell no, and he actually did a good job at it. What I don't like is Lucasfilm and GL lying and saying it was all planned, when it was not.