Yeah, see this is the problem with or group as well. We have so much time in between games that a given plot or story for one campaign gets forgotten or pushed aside for new ideas later on. If we try to run the old game, everyone is excited about some new concept and ends up not paying very much attention to the current game.
Our solution: Run three campaigns at the same time! This basically allows us to finish of a brief adventure with any one game and switch if the mood takes us elsewhere to an entirely different collection of characters, different plot, differnet "feel" etc.
You can even ave a differnt DM if more than one person is interested/capable of taking that role...
There are trade-off of course, but this seems to be the best solution for such an intermitant gaming schedule.