I've been in a number of roleplaying campaigns since joining the hobby about ten years ago, but I'd never really played a campaign to completion until my second year with GUGS. Since then I've been in four campaigns that I saw through to the very end: a Call of Cthulhu mini-campaign based on The Black Drop adventure for Trail of Cthulhu, James' 'WoD: Demonocracy', Doc's 'Marvel Multiverse' campaign, and James' 'L5R: Sins of the Family' campaign.
In the past, I'd either been in short campaigns that fell apart or petered out before finishing, or in long-term campaigns that I had to drop out of due to my workload at university or poor health. Also, two of the main campaigns in the society I was with previous to GUGS were open-ended drop-in campaigns - one set in the Warhammer Fantasy world and another in a homebrew supernatural setting - and I never really got the opportunity to play a retirement game for my characters in those campaigns before moving away. And then there were some online campaigns, which either died off from lack of participation (mostly PbP campaigns), or fell apart due to disputes between players, or GM burnout.
Now that I've actually been in some completed campaigns though, I'm wondering now how many games actually fail to reach a satisfying conclusion. Was it just bad luck that the games that I was in before didn't make it all the way to the end, or is it actually rare for games to be wrapped up properly? What makes the campaigns that get finished more successful in doing so than others?
Well, from my own previous experiences, here are the things which usually lead to a campaign falling apart:
Real Life: This is really the biggest one. Much as we enjoy roleplaying, we have more important stuff going on in our lives. Some people have jobs, and within university-based societies many players are students with essays to write and exams to study for. And that's just the stuff that we can anticipate, there's a wide range of circumstances that can catch us unawares: illness, injury, invitations to weddings or funerals, and anything else that I just can't think of this early in the morning. (It's 8am as I'm writing this.)
GM Burnout: GMs are not all-powerful game-facilitating deities - despite what some of them might like to think - they're just people like the rest of us. And running a game can be a challenging task, from dealing with problem players to juggling different story arcs, writing up stats for NPCs and trying to keep things moving forward according to schedule, and scrambling for ideas when the player characters do something you just didn't see coming. It can be stressful at times, and sometimes, if it becomes more like work than play, the GM will lose their will to continue. It might happen gradually, with the game grinding to a halt as the GM becomes more apathetic, or suddenly if the GM has a panic attack during a session and has to quit there and then. One way or another, if the GM's fuse blows, the campaign is probably going to go bye-bye.
Player Committment (or lack thereof): I already talked about how real life takes priority, but sometimes the problem isn't just real-life, but player committment. Maybe one player's just not getting into the campaign as much as the other players are and they're drifting away from it little by little. Or maybe real life is very hectic for them right now and they're trying to have things both ways, but they're absent from the gaming table more often than not. Whatever the reason, if players make a habit of not showing up and they don't let the GM know they're going to be less involved, it can cause problems. The GM might have prepared material for the campaign aimed at a specific character which has to be put on the backburner - which can be a problem if its tied directly into the campaign arc - or maybe the GM wonders if the player is avoiding their campaign for some reason and doubt starts to creep in, which can lead to GM Burnout (see above). And it gets worse the longer the GM tolerates it and leaves the spot open for that player, because the player has either said it won't be a recurring problem or the GM doesn't want to risk offending the player by asking them to retire from the game. This leads us to another issue that might cause campaign breakdown.
Failure to Communicate: Whether it's on the GM's side or the players' - or both - sometimes a lack of communication can lead to problems that will cripple a campaign. Maybe the GM hasn't picked up on what the player is looking for in the campaign, maybe they completely disregard the player character's backstory to suit their own ends, or maybe they're just struggling to figure out what the player wants to do. Maybe the players have misunderstood what kind of tone the GM is aiming for, and take a completely different approach to things than they had in mind. Whatever the case, everybody is looking for something different in the campaign and their interests end up clashing. And speaking of clashing...
Personality Clashes and Problem Players: Sometimes, some people just don't mix well together. Maybe your GM turns out to be a bit of a douche, or maybe one of your fellow players is a little too keen on having his character chopping up NPCs into little pieces for kicks. It could be anything, but for some reason your group just doesn't get along, and that situation's only going to get worse the longer you play together. If the GM is the problem, you're just gonna have to leave and find another game to join. If it's another player, you can try and resolve it between you, or the GM can have a chat with them about their in-game or out-of-game behavior. If that fails, and the GM doesn't have the heart to kick out the problem player (assuming it is just one player) then the game just isn't going to be fun, and people will end up leaving.
Bad GMing: I've hinted at this already, and I don't really like to say it explicitly, but the fact is that some people are just horrible GMs. Maybe they have their own ideas about their campaign and hold fast to those ideas, disregarding the interests of the players when they don't fit with their own. Maybe they're too heavy-handed in action sequences, leading to an inevitable total party wipeout. Or maybe they take their campaign in a pretty skeevy direction which the players just aren't comfortable with. In this case, you probably won't be mourning the campaign itself when you leave - or it falls apart - just your lack of a campaign to play in.
These are some, but probably not all of the reasons a campaign might fail. Some can be avoided through better communication, being supportive of your GMs and players being honest with themselves and their GMs about how much time they can put into the campaign. Others are trickier, like clashing personalities - and there's really no way to avoid real life. That's just something you have to deal with.
So, how many of your campaigns have actually reached a satisfying conclusion? How many have fallen to pieces? What's the ratio of completion versus failure? And what causes for failure have you experienced?