As Battlestar Galactica, once the best science-fiction show on television, painfully limps towards its three-part finale, the question which poses itself is: where did it all go wrong?
In the original miniseries and the first two seasons, Galactica managed to combine science fictional concepts, space adventure and realistic, multi-faceted characters to an unprecedented degree. Season three started off equally strong, but lost its way in the second half of the season. And the fourth season is drowning in autoparody, weighed down by an ever-increasingly complex and nonsensical mythology, which deliberately raises five questions for each one it answers.
Where have we seen this before?
Oh yes. In the X-files. Instead of providing answers, Chris Carter and co piled on the questions. By the end of the show's ninth season, nobody cared anymore, a painful end for a series which had been a real pop-cultural phenomenon.
Ending a long-running series (with continuing storylines) in a satisfactory way seems to be very difficult. Alias, which started off so well, was nigh unwatchable near the end. Prison Break, which had probably the best gimmicky concept ever on television, managed to lose everything which made it special from season two onwards, and had to wrap everything up in a truncated fourth season.
However, not all series end on such a low note. The Shield had an effective series finale, for the most part. So did The Wire. So did Deep Space Nine and, to an extent, Babylon 5 (which only ran into trouble because it had already used up all its material by the end of season 4 in order to finish the story when cancellation seemed likely).
So what's the difference? What's the reason for one show to bow out on a high note, while others seem to lose the magic they once had, even though the same showrunners stay in command?
In most cases, not knowing where you're going is to blame.
During the X-files' run, it was so obvious that the backstory of the various conspiracies/invasions had not been fully thought out. When I aired this observation (during season 5, I think) in class, one student, an avid fan of the shown, reacted with shock. She couldn't believe that the makers of the show would let her down like that. Well, they did.
And on the commentaries, Ronald D. Moore, Galactica's showrunner, has admitted several times that the show gets made up as it goes along. Which is really a dangerous track to follow once you start messing with prophecies, characters with special destinies, a hidden Final Five group of Cylons which turn out to be regular cast members... The feeling of humanity on the run from an implacable enemy, which may or may not have a valid case for its vengefulness, has been lost completely in all the sub- and counterplots.
Similarly, on Alias, the Rambaldi legacy which drove all the machinations by the various secret factions on the show, was never really determined until the very last episode. And then it turned out to be the least inventive solution to the mystery - it was a simple recipe for immortality.
Knowing where you're going, how you want the show to end, what the true nature of the mysteries behind everything is, is essential if your show is to keep its vibe and vigour. So what if fandom guesses some of your ideas? You can always adjust as you go along, if necessary. But working blind, as it where, just trusting to fate that the brilliant idea to tie everything together will show up at exactly the right moment... that way lies disaster.
It's like the Boy Scouts say: be prepared. And the better you're prepared, the better the end result is likely to be.