Good stories hurt the longevity of an MMORPG?

For many people, inlcuding myself, a good background story and story content is an important aspect of an MMORPG. So why the headline?

Let me qualify “good story” a bit; that is that a game company developed story is a prominent feature of the game and with some thought to hold various elements in the world toghether by the story. You have to put in an effort to compltely avoid the story, if you wanted.
Tabula Rasa is a recent example, Earth & Beyond was another game with some serious story telling ambitions. LOTRO is another one in the fantasy genre.

The story experience if often considered weaker in MMORPGs though compared to single player games. In single player games, the player is the big hero or center of attention – this is not the case in MMORPGs.
The story telling is however not much different from single player games. At any given moment a single player can experience the story by himself/herself. He/she may need help at certain stages to overcome certain difficulties but in essence much of the story telling is just directed to a single player – no element of the story changes regardless of the number of players involved, only the amount and diifculty of some enemies in the path of the story.

Thus I think the story telling currently works better to support solo play experience, sometimes spiced up with some added support by other players. It does not support a core multiplayer experience, at least not well.

And for longevity of a player experience in an MMORPG, the multiplayer part needs to work. This can of course be accomplished by other means, but the story as it is now does not do that much to contibute to it. Rather it makes the solo experience better/good/more bearable. With a too strong story element in comparision to other features of the game, the game is going to hurt. To some extent like in single player games, players are going to feel some kind of completion when a story is followed through. And that may make the game feel “empty” and people may end up quitting.

Compare the games above to games like World of Warcraft, City of Heroes/Villains and Everquest 2, to take a few. The latter 3 all have a strong background story element, but the story element is a bit more hidden and a less prominent part of the player experience. I think this provides for a better foundation for longevity of the game as it is now.

And then there is EVE Online of course. Not much story at all provided by CCP, but very much so by the players themselves and very much a multiplayer story telling. And for those who get into EVE it seems to last quite well.

So how can the story telling be improved? Does it have to be player created content only, like in EVE? Or can game companies create story telling on a multiplayer scale and will that keep players playing longer due to the story?