Longest Campaign Played
I was in two minds about this one. When it comes to tabletop play, I've rarely had much luck... Maybe fifteen-or-so sessions has been the largest number of continuous sessions for a single story. But in sheer timespan, I did have a campaign that was only played on solstice nights for a while, and six stories of that game lasted almost four years (because we couldn't get together for some of those sessions).
Then I remembered my time in the Live Action Camarilla global campaign, where I was both a GM/Storyteller and player. This saw fortnightly games (with multiple games occuring each week at the most regular times, monthly games at it's slowest), and was a part of my life for about five years in one form or another.
I've vaguely come into contact with one of those epic "fourty year chronicles", but I do know of a group who started playing a campaign in the 70s and are still playing it to my knowledge. I've sat in and watched one of their sessions, I've even taken part in one of their crossover sessions at a convention (where the convention players are allowed to dip their toes in the vast setting they've developed over the years). But I certainly can't say that I've been regular in that group.