I've never done that. It never occurred to me. However, with my newer machine, it automatically stops exactly where the bobbin runs out and I put a new one in and it picks up right where it left off. I throw the thread that's on an old bobbin on my older machines out if I don't have any empty ones available. But now I have so many different types of thread and sewing machines that I'm having to keep the bobbins for the different machines separate...and then I have to keep the type of thread on the bobbin separate too. So I just have bobbin cases next to each machine so I don't get confused. I can tell the type of thread just by looking at it.