I agree with everyone else. Unless it breaks easily, it is fine. Cotton threads and cotton fabric like the same living conditions we do: room temperature year 'round. So unless it's been stored in the attic or some similar place with horrible temperature fluctuations, it should be fine. I'm pretty sure I read somewhere that thread is best stored in a 50% humidity environment. Congrats on the great find! :thumbup:

If it has any polyester content, it will be stronger, polyester lasts forever. Cotton is a natural product and does break down, but since it has been in a bag, that would have protected it. I would use it if it seems strong.

age doesn't really have a whole lot to do with it- i've used threads that were 20+ years old & they are fine- i've had others i bought last week- that are not usable...
it depends on how they are stored, and the thread itself much more than the age- & just because you bought one last week does not mean it didn't sit around in a warehouse or store room for 10 years before going out on the shelves.
do a strength test- if it's still strong enough to use it's fine to use- if it breaks easily it's time to replace it.

A sewing machine repair man years ago told me 'if your thread breaks just put in the frig for a while and it will work fine' tried it and he was right,, give it a try....it just needs moisture in it.......

I agree that testing is the solution. I am working with thread that are over 30 years old . I mostly use them mixed with newer one on the overlock m/c but sometimes with the rare colours I use in projects and so far so good :-)

Thanks for all the responses. The two I have tried seem to be just fine and it was a nice surprise, since I have been trying not to shop so much. Still can't figure out why I put them in the pantry or how I missed that bag for the last few years.