I have a number of saves, most of which I use for exploring, testing, and/or developing story ideas. Sometimes I play out some of the parts of a larger story in separate saves and then import the characters (and their homes, if it's important enough to their stories) into another save (where the main story resides). Some saves are more for testing game mechanics or technical things (like to experiment how one mod interacts with another, etc.). I currently have three "primary" saves that act as staging areas to bring all the parts together for three different overarching themes, and each of those has one or more "secondary" save to "feed its master", as it were.