I used to save the bobbin thread until I had too many bobbins with colors of thread that I was not likely to use in the near future and I needed a couple of bobbins. It dawned on me, the price of the left over thread was a lot less than new bobbins. And with my learning curve on my embroidery machine it was a good thing I was no longer worried about wasting thread, I wasted a LOT of thread. :-)