After a couch has been lived on for a few years, it will likely begin to show some wear. If the sofa cushions are sagging, replacing the foam in the cushions can give the sofa new life. This is a project that is done with minimal cost and time, depending on the size and design of your couch. This is also an effective way to refurbish sofas with removable back cushions as well as seat cushions.
Purchase sofa cushion foam or cotton batting at a craft store, or use foam from other, discarded couch cushions. If looking for foam replacements, used couch cushions work well, though they may have to be cut to fit. Otherwise, high-loft cotton batting provides a reliable fill, and additional batting can be added over the years to maintain a comfortable loft.