I use my own filled at some point bobbins up.
I bought a cabinet last year that came with a machine whose bobbins had from 8 to 11 different colored threads on it. I decided it was just the difference in what the machine was used for, mending...or sewing.
I take it all off and fling it from me. As mentioned it draws moisture, the last thing our metal bobbins need.
You could add it to your ort jar...everyone has one of those, right?
This one is now
http://kalamaquilts.blogspot.com/200...e-ort-ort.html 3/4 full and shows clear stratifications from the various hand projects over the years.