I have powder that's 30 years old from when I first started reloading.
I simply tried other things and forgot about it and two others a few years younger.
All three were tested 2 years ago and worked fine. The powders have always been stored in original containers and in climate controlled environs.
I found some 18 year old primers in my Fathers stuff just last year, worked great. The price tag was still on there, boy has reloading gotten expensive or what?