Keep powder in factory containers and sealed, primers in their respective containers, bullets as I mentioned above. Prefer should last years after being opened if you only open it when pouring some out then recap immediately. My father has not had any problems in 50 years or so of reloading and he stores his stuff same as I do. If you are worried get a blast proof paint and chemical storage cabinet-i think somebody else mentioned that-but doesn't seem to be necessary.