would like everyone's opinion... not a safe, but a gun cabinet... what is the ideal range of acceptable humidity with house temps running from 65 to 70's?
Depends, are most of your guns wood stocked ? You can get it too dry for wood and will eventually crack them. Synthetic stainless I don't think it matters as much. I keep my safe at about 50-55 percent. I keep a bare piece of carbon steel in there and watch for rust, anything will show up first on that before your valuables.
Arclight nailed it, as did hlee. Actual numbers are arbitrary. The key is to keep the cabinet at least 1 degree warmer than ambient to prevent condensation, and thereby, rust, from forming.
Rope lighting from Home Depot. Have been using this product for over 25 years. It keeps the safe warm & dry as well as lit so I can find exactly what I am looking for when I open the door.