Look on the package and see if there's a "best by" or "use by" date on it. Let that be your guide. Just a guess off my hip, probably is okay. Check the date anyway, though, and make sure the packaging hasn't been breached. If the package isn't fully factory-sealed, you could have a problem. Submerge it in water and see if you detect any leakage, etc.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!