Not enough bobbins

Close to the end of quilting a customer quilt, I realized that I had not prewound enough bobbins. Sigh.. IT is always a puzzle trying to estimate how many I will need. I know it depends on the size of the quilt, the thread, and the design I am using. But not getting it right means I will have to UNthread the machine to wind the additional bobbins , and then REthread the machine. sigh... My husband bought a box of 100 bobbins for me for Christmas, offering the advice to just fill them up and make extras. So far, that hasn't worked. I have one or two of many different threads left, and I still have to guess. And the bobbins are disappearing.  sigh..... But that box of bobbins was better than candy as a present.