My apparel machine has multiple bobbins because it has to match and I dislike emptying and filling a bobbin. I
will wind a second color if the project isn't big and I don't have an empty bobbin available. My piecing machine uses pale lilac in the bobbin for almost every quilt so it doesn't need many bobbins. I do wind thread back on a spool for various reasons, but my quilting machine uses those on top so they are under control. When I come across old thread, I test it for breakage. If it passes, I keep it, otherwise it's pitched. I belong to the "I might need it someday" camp, but not if it's an inferior product. My grandchildren think I'm a hoarder, but after seeing that show, I know I am not. I do have too much "stuff" but it's all clean and usable!