Sometimes even new thread is not usable. Age isn't that much of a factor. My mom bought out a store closing stock of thread back in the end of the 80' s we are still using that thread. Once in a while we find a spool that doesn't pass the { tug test} but most is fine. Give it a tug test, if it passes try it out, if it doesn't break/ shred you are OK. How well a thread ages depends on how its been stored along with its quality in the first place