I've been kicking around an idea in my head lately. It was spawned in part by thinking about the abbreviated television seasons that shows on USA and SyFy have (inspired by the same shorter TV seasons for shows in the UK). While I am certainly in awe of people that can run a campaign for years on end, I know I have gamer ADD.
I run into too many different RPGs and have seen too many cool settings and ideas for campaigns to think that I will ever again run a campaign that has a lifespan measured in years. I've also been thinking about how long it really takes to get a good head of steam going, how long it takes a big plot to develop, and how long it takes to get a "feel" for a game system and how characters grow, change, and develop in that system.
Tentatively I'm thinking that breaking down a game system that isn't level based into about a 12 session "season" might be the way to go. This wouldn't be a hard number, and if something happened and the PCs ended up not able to resolve the big issue of the campaign that has been building up for months, we wouldn't say, "sorry, I'll need another episode to tell this story, but we won't get back to this campaign for a year or so, so no resolution for you."
While I've been avoided some of the more traditional ones lately, I thought about level based gaming systems and this mindset as well. I think, by design, characters develop differently in level based systems. I'd say under most I would at least run 24 sessions of a level based system to get a good "feel" and to let a serious plotline develop.
Finally, there are always oddballs. While I'm getting the urge to move away from pre-published adventures so I can cut lose a bit more with the creativity again, running Marvel Heroic I would certainly still use Events. The structure of events, as far as I have seen, is so open that the event is as much of a setting as it is an "adventure path." In the case of Marvel, I'd keep more of an eye on how many sessions I thought I'd need to resolve the Event, and plan accordingly.
13th Age is a level based oddball, as it's advancement isn't based on experience points, but on how many sessions the GM wants to run before he tells the party to level up. In this instance, I'd be inclined to run with two per level, to get a nice spread of 19 or so adventures, almost as many as I'd devote to a regular level based game.
Having an idea of how many sessions I'm going to run, total, gives me an idea of how to pace the campaign and can let me set some milestones as well. If I want to hammer home something that is a recurring "thing" in the campaign, but don't want it to be ever present, I should probably hit that theme about three times in a 12 session campaign.
If a major bad guy is going to spin out of the early part of the campaign to take center stage by the end, I should probably foreshadow his involvement or importance by the time I hit the sixth session or so.
I know, looking back, that if I had had in mind that my Rogue Trader game was going to go 12 sessions (and unfortunately we didn't even hit that milestone), I would have had a better idea how to pace endeavors and some of the plots that I was trying to introduce into the game. I had the overall concept in mind, but the pacing never took off for me.
All in all, I probably added several sessions worth of "padding" to my DC Adventures game that could have been edited out if I hadn't been trying hit the magical "over a year" mark for running the game.
Most of all, if everyone knows going in that we'll shoot for 12 sessions or what have you, it might be easier to plan out that we'll take a break from this game/setting, do another 12 sessions, then potentially go back to the originals, when everyone has had a chance to get a better idea what do do for the next "season," including the GM.
It's an idea that intrigues me to explore, even if it can be tricky to implement.