I DM the 'Dead of Winter' Greyhawk campaign online in PBeM format. The game started in September of 2000 and is still going strong. I still have all five of my original players plus three more that have been added in as time went by and my grasp of the game concept solidified more firmly in my head.
The game's success is due largely to great players, a strong pregame screening process, and an indepth plot of civil war and betrayal set in the eastern Flanaess.
Cheers,
Tempest