I put an 870 Wing Master in an eggshell foam lined case, put it into a storage building. Forgot about it for 8 years.(Non climate controlled in Central Texas.) No rust on it at all. I wiped it down with ballistol before I cased it. I cleaned it in about 20 minutes, and was shooting by the end of the hour. I still have it in the corner of my bed room by the bed for home defense.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.