Taste it. If it tastes fine, it is good. If stored dry and bug free, it will keep for many years.
I have a lot of specialty grains, and some get left for years. I'll still use it if it is 5+ years old. My base grains get used within a couple of years. I think I did toss some recently, it was from 2000, I'd been avoiding using it for years because it was so old, but thought ..... I might just need this .... It just got too old. It didn't seem bad when I tossed it.