In the later 1970's I finished shooting off a keg or American Deadshot Rifle Powder. Since the American Deadshot plant blew sky-high in 1898, this was old powder- not quite 100years old, though, at that time. The powder was the best powder I had ever used. It was VERY Accurate in my Bauska .50 slug barrel and quite clean burning compared to the GOEX of the day. I shot a number of 1" to 1 1/2" groups with it at 100yards using match-type aperture sights.
So - 30 year old powder - is it good - could be?
If it works well, if so use it.
Seems to me, only the phony powders like Pyrodex chemically degrade. They degrade in loss of power. Not so, with BP.