Sheet Set Manager (SSM) is a very powerful tool, but with its power comes a degree of complexity. The average end-user should never have to dig into the back end of SSM, and have to set up fields and the like. On the other hand an average end user will use the "Sheet Management" functions on a daily basis. Note the usage of "management" in that last sentence.
The average user has a preconceived notion that SSM is first a plotting tool, and second a tool to fill out their titleblocks. Although both are strong functions of SSM, it is not the boundary of SSM's limitations. In many ways SSM is like a miniature "Windows Explorer" within AutoCAD.
Say for example you need to rename the filename of a sheet contained in your set. Go to Windows Explorer? Not so fast pal! If you rename a DWG that is linked to your Sheet Set, you will soon find [?] marks next to all of your sheets. The? mark next to your sheet of course means that the link between SSM and the actual file have become broken.
To avoid that, rather than going to Windows Explorer to rename your sheet files, use the "Rename Renumber" function within SSM. Using that function will rename the file, and update the SSM reference to it.