I am guilty of all of the above---winding too much over what is already in the bobbin thinking I'll use it all on my current mending project (that's all I get from my kids anymore--their mending); then leaving it on the bobbin when I change to another color. But my bobbins are Elna, so I can tell if there is enough left on it to finish something. And I have been known to strip all the thread off if I know I'll be using a bobbin off. And for piecing, I use up whatever is on a bobbin no matter the color, until I get disgusted with running out of thread when I have sewed up half a strip of 2-1/2" fabric.....then I'll fill a bobbin with a beige or gray like the rest of you ladies seem to do. Not a nickle's worth of difference in any of us, huh? Must be depression era kids.....Love you one and all.