I think I was the one that posted I don't use old bobbins. Let me add more details of why. For one thing I like new bobbins.
It's just a sewing eccentricity I have. Nothing wrong at all with most old bobbins.
But plastic bobbins can have small cracks and scratches after many uses. Metal bobbins if dropped can get out of round. Most times I have had terrible bobbin thread issues, when I changed to a new bobbin the problem disappeared. I wind older metal bobbins with all different color thread and keep in bobbin holder for hand sewing binding or yo yos or mending. Over the years I had way to many filled older bobbins so I started giving filled bobbin rings as gifts. A silicone bobbin ring with filled bobbins of different colors of Aurifil thread will make any quilter's face light up. Another reason to buy new bobbins and fill the old ones.