The answer is about 11,000 yards.
I started quilting about 2 years ago, give or take. I think I've kept almost all my empty spools. There are quite a few used spools, that I haven't emptied yet, so the real number is bigger, but almost 11,000 yards of empty spools is pretty impressive. I asked the Hubby how many yards of thread he thought I had used in 2 years. He guessed 1,000 and was very impressed by the actual number. I think I should let the empties go now, what do you think?