I also read an interesting interview with Lois McMaster Bujold in which she talks about writing books in a long story arc. She mentions that one reason she doesn't like to write in a traditional "series" format (i.e, with the same characters) is that the "...readers only have to live closely with the characters for the day or two it takes to read the novel: I have to keep them stuffed in my head for a year."
So, the appeal of the long story arc allows the writer to build depth into characters, but too much depth can lead to author burnout. Bujold solves that problem by reusing the world but varying the cast. In Dr. Who, the writers can vary the Doctor's companion and even the Doctor himself. After all, he changes personality when he regenerates into a new body.
Bujold works in novels, and the Dr. Who writers in TV episodes, but it's all still story telling. Fun for the reader/watcher, and fun for the story teller!
