If it seems usable.... Use it!
If the powder doesn't smell acrid, isn't changing color, and isn't breaking down, it's probably fine (though it should be kept out of sunlight, if you want to prolong its usefulness -- glass jars are not approved storage containers, and are not good for powder).
Prime a few cases with the old primers. Set them off in the empty cases. If things go well, try a few loads with them. If that goes well... load the stuff.
I currently have about 60 rounds of .243 Winchester that was loaded between 1963 and 1969 (reloads that were given to me). Certain years I have found to be bad, due to case lube contamination. Other years are just fine.