Although the final word is not out, it is becoming increasingly clear that the way to get a "full story" out of a sci-fi franchise is to do it all in one season. Certainly, it should be possible to make 22-hour stories that are totally fulfilling and complete; if we can do a movie in 90 minutes that feels right, we should be able to do a TV show.
If the creators refrain from a *catastrophic* wrap-up, then there is always potential for Season 2 as well.
The problem with the model is not that "only the good die young". First of all, what I think is good and what others think is good might not be the same. I have no objective standard; I just (like everyone else) happen to think I do. If you believe that shows fail because they sucked, and you think, for example, that [your favorite show] jumped the shark at point [X]--and that is why it was righteously killed off -- you are not paying attention. Fan-rage is not just common -- it is a given. If you are the sort that invests too much in a show and then repeatedly feel let down by their demise (either by cancellation or by a storyline you don't like), the problem isn't "them" or the bovine-minded masses who you feel accept the studio-created pabulum. The problem is you -- specifically your expectations combined with a belief that it is "bad shows" that are canceled where "bad" means anything other than "unprofitable.
Second, the problem is not fan-communities; all of these shows have vibrant fan-communities. They are organized and socially networked. The problem is that the estimated millions that it costs to produce a TV show are not supportable safe by wide-scale advertising. Furthermore, the TV studios tend to most-heavily weight live eyeballs during prime-time. If you are DVR'ing, you will skip past those commercials. If you are getting them from Hulu or the company's site, you are perhaps evading all but a single advertiser.
If you are torrenting them, you never see any commercials at all.
This means that a show can have both rabid fans and sufficient eyeballs; and if it shows Friday night to a young crowd who are all out Friday night, then it will starve for ratings. Combine this with the need for heavier F/x in science fiction shows (almost by definition), and you have a serious difficulty in creating continuing content. The stakes are, I am told, very high. A hit show is a gold-mine; so, like a miner looking in different potential veins, the studios are reluctant to carry a poor performer since there is a chance the next runner-up could make them filthy rich. Given those odds, you probably wouldn't bet on an under-performing horse ... even if it was 'really pretty'.
So what can we do? Well, there is one thing that is pretty clear to me does not work, and that is fan protest. I am unaware of any show being saved by the fans, and while Star Trek did come back, I think that you have to remember that by the time Next Gen came out, there were already several movies in the stack. It wasn't that the studios didn't think the franchise was valuable at all; it was that they lacked whatever it took to make a show of it and some guaranteed response wasn't enough.
Also, if fan turn-out could not save Firefly, I am not sure what it would take. It wasn't that Firefly was so great (although it was); it was that the fans had a real, serious, coordinated effort in conjunction with a knowledgeable and moderately powerful creator, Whedon, who was paying attention. If Serenity had been a box-office smash, we might have season 2; but it wasn't. Fanatical loyalty doesn't save shows; it takes broad lukewarm appeal -- probably people tuning in when other things are going on, e.g. folding laundry.
It could also help to have a low budget, but, as I said, science fiction suffers more for that than other shows.
On the plus side, though, there is no reason at all that a 22-show story could not totally rock our worlds. We have already seen the format in 24 and the Spanish language novellas. These shows put out a single story with somewhat original characters that wrap up the plotline by the end of the season, sell the DVDs and then move on.
I think this is what I would look for next time. It is certainly better than watching the Dollhouse wondering if Echo will ever get out or even if she should -- knowing that a last-minute wrap-up is absent. Note: Apparently Fox will air the last Dollhouse for this season - most probably the last season -- only on the DVDs. This is presumably to force you to buy them. I don't expect Terminator to take us through to Judgment Day, but I would at least like not to see it peter out when there are so many stories I would like to see resolved.
This also makes me hesitant to get involved with other franchises. I stopped watching Heroes after a few episodes into Season 2, and while it might have gotten better, I am glad I removed all emotional investment from it. Its longevity is in such doubt that if I were rooting for it, I would probably be disappointed too.
