I have some primers and powder (unopened container) that are somewhere between 5 and 10 years old. they have been stored in a climate controlled environment. Can they still be used?
If properly stored as you describe, they should be fine for several decades. I'm using powder and primers I purchased in the late 1980s and early 1990s, and I'm sure others will come along to say theirs is much older than that.
ranger your powder is fine if unopened and will last a lot longer if left that way. I will tell u a story that will explain some of your worries about old powder. back about 10 years ago at the super shoot i found a killer deal on n133 from the vihtavuori dealer. me and a friend bought 4 jugs each and as common with benchrest shooters after we got home mixed all together and then redivided and stored. now the only difference is i do my reloading inside and he does his in garage(no a/c). about 5 years ago we happened to meet up at a match at riverbend in atlanta and he asked me was i still shooting that same powder we had bought earlier and i said yes. he asked did i have any problems and i hadnt and he told me his powder wouldnt hold single digits over the chronoghaph any more. he tried some of mine and back to single digit spread with virtually the same loads 29.3 vs 29.4. the problem came when he introduced the lot to high humidity as its not uncommon to get 100 percent in north fla. 3 things that will affect powder over time and thats humidity temperature and light,hope that helps