The Sum of a Campaign Is Greater Than Its Modules

One thing I think nearly any role-playing campaign can benefit from is the opportunity for unmodules (q.v.). Unmodules are what I used to call gaming sessions in which the player characters pursue whatever activities they desire, free of the obligations imposed by a previously written adventure. There is something satisfying about the ability to chase a personal goal in one's free time, regardless of how heroic or safe it might be. It helps round out a character's personality and enables players (and their characters) to enjoy the fruit of their endeavors. In short, it makes the campaign richer and vastly increases the players' investment in both the campaign and their characters. The more the player characters do in their spare time, the more hooks they will provide the GM (wittingly or unwittingly). The more unmodules you run between adventures, the more you will create a true campaign rather than something that feels like a series of one-shots.