Some fans do have a tendency to forget that the creative folks they love are not simply black boxes, who produce desired product at regular intervals. They’re actually real people who do other things than just what the fans want them to do, because humans from time to time want to do the things they want to do, not the things other people want them to do. Yes, some fans don’t like that, but you know what, screw the type of fan who thinks a writer (or musician, or actor, or whatever) exists only to provide them with the entertainment of their choosing.
I’ll go personal here and talk about my own experience. As most of you know, the books in my Old Man’s War series are my most popular ones; each of the four novels have done very well and even the shorter works are pretty popular. There are people who would be delighted if all I did was write OMW universe books from now until the hopefully long-future date at which I drop. But thing is, at the moment, I have no plans to write any more OMW books. It’s not to say I never will, if I figure out what I want to do with that universe from here. I expect I may. But at the moment: Nope. I’ve got other things I’m working on which at the moment interest me more.
Now, I know this annoys some people — my matrix of ego-surfing search engines alerts me to many incidents of fan entitlement, particularly as regards the OMW universe — but I don’t think they understand what they’re asking for. Yes, I could write OMW #5 at the moment, but I guarantee it would suck, because at the moment I don’t know what I would write about, and thus OMW #5 would simply be a bit of commercial hackery, and it would show. And these same fans would say “Yeah, the series used to be good, but then he started phoning it in around book five.” You know, if I’m going to annoy a fan, I’d prefer to annoy a fan by not writing a book that sucks, than by writing one that does.
These are all points well taken. I'd only have a couple of rejoinders: first, I'm not sure the OMW books of Scalzi's are a great counterexample, since they're self-contained books; if he never writes another, he's not leaving anyone clamoring for the end of the story. Second, I do think that Martin has himself set up a lot of the bad feelings by periodically making overly optimistic appraisals of his progress on Dance, and by setting up the structure of Feast so as to imply that Dance would come along in pretty short order. Fans no doubt fear that the next book after Dance will take an equivalently long time, and there's no telling how long this series will become when all is said and done. I have a feeling that this series may end up going unfinished, and that would be a shame, even if I was disappointed a bit with Feast.
But this sort of thing is hardly new in the art world. Here is Richard Wagner, writing a letter in 1851 about his new project, an opera based on the legends of the Nibelungs:
With this new concept, I sever all connection with our present-day theatre and its audience: I make a definite and permanent break with present-day forms. Would you like to know what my intention are regarding my plan? In the first place, to carry it out, so far as lies within my power as poet and composer. This will take me at least three full years.
So, in 1851, Wagner was figuring on three years to write his Ring Cycle. When did he actually finish Gotterdammerung, the final opera in the cycle? Not until 1874, twenty-three years later. Of course, Wagner didn't have legions of fans on the Internet clamoring as to his progress, which is the only thing that's different, I suppose.