There are a number of muds which implement end of game conditions, but frankly it's been so long I can't remember their names. I believe there was an LPMud that would run for around a year, determine the winners of the game, delete all the players, close down for a few weeks and reopen with updated content.

It also not uncommon on Mushes to run a campaign during a particular time frame and after it runs its course start a brand new campaign for a different time period. The second campaign building on the history of the first campaign but often with all new, aged characters, or with descendents of some characters.