That is why you clean out your farm seed out of your bins before refilling.
Always check out the back corner of a TSC for good deals, usually half price off.
Ah ok. So if it's one of the sealed bags it's probably OK for the most part. I had an entire 50lb bag of field rye that was kept in the garage go bad one year. Seed itself looked fine but didn't produce a single speck of green. The bag was paper so I assume fluctuations in moisture content caused most of it to fail if it was good to begin with.