I love running long term/persistant games.  Here are some thoughts of how to make a dedicated persistant world.

• Gameworld mapsize is maximum(unlimited if able), enrollment is limited
  • Required to register with server to setup avatar, login, and contact info
  • Rules/expectations are set and "agreed" to...with variables such as contact times, play times, etc
• Your character is created and located somewhere in the fog of war of all other still-active players
• Your game is "instanced" until your & another player's fog of war meet
  • At this time, if both players are online gameplay continues as normal multiplayer
  • If other player is not online, a notice email is sent to player(as part of registrating with server)
    • They have 48hours to be online the sametime as you
    • After 48(or parm driven time) encounters will be handled by AI. (only reactive encounters, AI will not be exploring/proactive)
• If a player is not online for xx amount of days, or doesn't have xxx amount of turns/playtimes they are turned over to be a NPC faction
• Gameplay can go on forever, creating new content within the fog of war. 
  • upon player creation, they can chose to create "new area" that is low risk, farther from an existing Player
  • or they can choose a risky "forgotten" area that will be remote located and fog of war gets reintroduced to areas after xxx amount of turns
• Of course, reporting and stuff
  • # of players, score, turns, size, etc...all that can be ranked but not give away too much knowledge to other players