When I sew on my Featherweight, every week when I oil, clean and change the needle, I fill 8 bobbins with the neutral thread I will use in the coming week. I do this because I am so left handed that threading the needle is not my idea of fun. I don't want to have to stop and wind a bobbin and have to re thread the needle. Once a week of needle threading is enough for me. On m Bernina, if I am doing FMQ, I fill lots of bobbins, otherwise, I just stop and fill the bobbin as I need it.