My longest campaign was my WEG Star Wars Elrood Sector campaign. I ran this game for the entirety of high school, sometimes multiple sessions in one week. This is my longest running campaign no matter how you measure it, length of time, or number of sessions. It was a great system and a great setting in the system. I revisited the Elrood Sector a couple of years ago when I ran an Edge of Empire game there. That campaign is another one of my all time favorites.