When I went through my first couple spools of thread instead of throwing them out I decided to keep them as they are pretty sturdy and I thought perhaps could be useful later on.
Then I started to go through more spools and now 6 months later we have a ton, probably around 50 or so but I think many of them are under the couch and my short arms can't reach all the way back to get them. But as you may have guessed I started letting The Bubb play with them a few months ago and he loves loves loves them.
He doesn't try to eat them anymore but he loves to roll them, bang them together, stack them, put them in drawers, put them in his box, stash them under the couch etc. They have turned out to be the best toy as he can't break them, they roll, are durable, and he loves to explore the inner spokes with his little fingers.
I have thought about painting them colors or wrapping fabric around the middle portion to make them more colorful but he doesn't seem to care that they are all white right now. But THE BEST part is he will roll these around the floor for 20-30 minutes at a time without needing any attention from me and is just so happy. (it might also help that either our floor is not level or these aren't perfectly round so they roll a little on their own).
Anyway I wanted to share cause if your kids love these as much as mine does it is just the best thing ever! But you will start to find them everywhere...