I have stored guns in soft cases, hard cases, and a safe. The general rule is to keep these things in an area that is cool and dry, and oil them once a year or so. My hard cases have gotten oil saturated over time and this leaves additional oil on the surface of the gun.
One area that I watch out for is back in the day I had so many military bolt action rifles that I stored them behind my bed on the carpeted floor in soft cases piled on each other. They seemed to go dry faster than the guns in the safe, in other words, oil would seem to disappear from the surfaces of the barrel, action, etc. I think there was some air movement in this location, but I would simply reapply oil every 6-9 months to protect them.