Should be good if no sour smell and no clumps. A basement is a good place to store powder due to lower temps. just as long no moisture got to it while sealed in the can it should be good to go.
I have some surplus military H4895 and H4831 that is over 40 years old and is still good. Got it from my father in law and he bought it in 8 pound kegs in the 60's.
RELH