Each of the books means something special to me because of what it took to create it. Same with the characters. But my attitude about both books and characters is that once they are fully formed, they don't belong to me anymore - they belong to the readers. So the readers have to make those decisions for me. How do you keep the well of inspiration from running dry after eight books . . .
Inspiration comes with time and distance.
Lester del Rey taught me years ago about the importance of dreaming your story first, of letting it percolate in your brain for a sufficient amount of time for it to take shape. So the trick is not writing too much too quickly in a series, but giving it time to grow. That's why I don't just keep writing Shannara books. Stepping away from the series for a few years at a time lets me dream about where it needs to go. It lets me recharge my writing batteries for those stories.