Powder usable life

[gaseous maximus]

I just got through using about 3/4 of a pound of unique (9mm & 38 spc.). I had the stuff scince the late 70s, It was among the remains of a friend's, girlfriend's marriage. it had sat a year or 2 in a rental storage unit,the kind that get really hot. was gonna throw it away but powder kept going up and.... any way it shot fine. ran it across a chrono. and it was right where it should have been.

 

[Roadking Larry]

It's been my experience that powder is only usable once. After that it is pretty much just smoke and residue.
I use a lot of Unique though, in .38 Spec. .357 mag, .45 ACP and .30-30.