Is this a good idea? I think it probably is. More than one show has gone on and on and on and, well, on, becoming by its series finale a mere shadow of its former self. In its third season, Lost is already starting to fray around the edges. Its complicated arcs are far from being resolved, and in this case that seems to be to the show’s detriment. You can only string the viewers along for so long without giving up the goods about the damn polar bears, after all.
It seems to me that a show like this, with serialized, complex storylines, actually could benefit from having a finite, predetermined end date. Lost might have developed differently if from episode one the creators and the network had known they had 100 episodes in which to tell their story. Of course, it’s not exactly easy to get that kind of commitment out of a network. Babylon 5 started out with a very clear idea of its five season story arc, only to get shafted right after Season Four. Season Five eventually was produced, but the show suffered from the turbulence. Farscape had been promised a fourth and fifth season, so the creators planned a story arc to cross those two seasons, complete with Horribly Devastating Cliffhanger for the end of Season Four. After all that was filmed, Sci Fi pulled the plug on Season Five, leaving fans hanging. Fan outcry finally led to the production of The Peacekeeper Wars, but the complex conclusion had to be compressed into a four-hour miniseries instead of the full season arc originally planned.
Would ABC be less willing to negotiate an end date for Lost if its ratings hadn’t dropped significantly this season? It’s hard to say. In any case, all the maneuvering and politicking make for a tough balancing act, and nothing about it is conducive to good storytelling. So when the good stories come out in spite of that, it’s just that much more impressive.