Unlike the old days when powders shipped in lined cardboard containers, the new blow moulded, inert, light blocking containers will preserve powder indefinitely (so long as they aren't opened and left open). Resealing the lid after using some with a sheet of plastic (zip lock bag section) under the screw cap insures freshness. It will keep stink'in for years.
I've got powders I use little of that are 10 plus years old and just fine.
Load 'em up. Let your nose guide yo. If it stinks, it's good.