Swatches, most often I keep them until the end of a project. Perhaps, using the yarn for seaming or a pocket. If large, just unravel and reuse in a different project.
Today, I needed a new flag at the end of my driveway to warn drivers of a sprinkler head.
I had painted my front door a spring green colour and a green flag might be nice.
When, I pulled out my green yarn, I noticed the swatch. Maybe, flag size? It was.