I am careful to use whatever bobbin comes with my machines. I can't remember ever breaking a bobbin (knock on wood here); but my machines are all in cabinets that have the bobbin holder thingy in one of the drawers; so that is what I am good at doing when I am sewing at a particular machine--thread color is not so important when I am in a hurry, just the right bobbin. I have one machine that will use plastic or metal bobbins; that is a 201, I think. I am a picture of OCD when I am teaching someone to sew on one of my own machines--making CERTAIN that he/she is aware of using the right bobbin in that machine. Plus, IMHO, speed sewing might be a matter to consider here. I am not a speed demon on any of my machines. Just my take on this subject this morning.