Ms Coffee, I had some thread that is older than dirt!! and believe it or not, it still works. Let's say it's 26+ years old (I owned a fabric shoppe). I've used it on occasion for machine embroidery and in sewing, if I needed a particular color. It's still strong. Most is Coats & Clark thread. Just test it, if it's pretty sturdy when you try to break it, it's good to go.
Jean