One of the good and bad aspects of an MMO is that it is a form of storytelling that does not really end in the same way that a consistent narrative does. A novel, a movie, even a single player RPG can have a climax in a way that a MMO like World of Warcraft simply cannot. Killing the Lich King isn't the end of the story, it's merely a chapter coming to a close in a saga that just keeps rolling along. Given enough time and the momentum of such a thing becomes its own literary device, effectively, as you know you'll be facing something new before the body of your current antagonist has a chance to cool down. (Of course, since you'll be rifling through his or her pants for some loot, how cool was it really going to get?)
We talk a lot about expansion gear resets, greens replacing epics to be replaced by blues we then replace with epics and so on. Frankly, I've come to see this as the great strength of an MMO and not something that holds you back. No matter how awesome your gear is now, no matter how epic the fights, no matter the towering evil you're defeating, tomorrow will bring new gear, new enemies, and new stories. Yes, it can be seen as a treadmill and us as hamsters running it, but it can also be seen as a ladder always going somewhere new.
So what about you? Do you like the limitless nature of the cycle, or do you want an endpoint? And what would you want it to be?