I think buttons reproduce while we're not watching.
I recently found a lovely new home for five collections of buttons--white, red/pink, green, blue, and yellow. I thought I was done. Oh no! I just went back through the stash to set aside buttons that I know that I cannot part with, and I was left with GIANT piles that need new homes. I have now listed four more sets on Etsy: black (200+ buttons!!), brown (160!), gold (101!), and silver (61!). I really really really hope that's all. Or they're all going on the pill.