Moisture control is critical. I've had to store guns on the Gulf Coast of MS, in a non-climate controlled garage. Granted the guns were in a Fort Knox safe, but the salt air is all invasive. Before my dad arrived from St. Louis, every weekend I had to remove, oil, and replace all the guns (14+ rifles, and 12+ handguns). As a teenager I could have thought of better things to be doing and the anxiety of dinging up some of the ole man's more expensive rifles.
That was extreme, nowadays it keep a Golden Rod dehumidifing rod in my safe, a little more fancy than the light bulb technique. I also run a stand alone dehumidifer in the room. Oiling and at least handling the guns at least once a month for inspection. My safe sits on some 1x4's to keep it off the basement floor.
Desiccant containers/bag are good also, the dad had a caninster which could be re-used by baking the canister in the oven to dry out the crystals.