I have lots of cotton covered polyester Dual Duty Coats & Clark thread. I didn't know about Aurifil, etc. until comparatively recently, but my machines are quite content with C&C. But then, all my machines are pre 1990.
My criteria is also - does it break easily? If yes, it gets discarded.
If you are "thread selective" - if you wish to donate or sell your Coats thread, I am reasonably sure there would be takers.