The LGS are air conditioned, so that controls the humidity. It would also depend on the finish of each gun. Finishes like case hardened steel would need a LOT more care than a stainless revolver.
I also put a thing of DampRid in my gun safe to help control the humidity in there. I've had some rust show up on a Rem 700, but other than that, no rust on any of my guns, but I also don't really have anything that doesn't come some sort of coating or treatment on the steel parts (Glock's tennifer, HK's corrosive environment finish, ARs, etc). I'll check the Rem 700 that showed some rust on the barrel and the rings and bases every now and then and wipe with some Ballistol, but that's about it.