Assuming that the powder wasn't stored someplace HOT it should be fine.
When last I knew the makers of Unique still had some from their very first lot. Every few years they would test a sample. Hasn't deteriorated yet and I think that they started making that stuff decades and decades ago.
I've had quite a bit of powder that was given to me new in the 70's. The last couple of years I've been shooting it up. Works just fine. Of course it was properly stored all those years but, still, age alone doesn't cause a problem.