(snip)...I keep my guns stored year round between 65-73 degrees and 40-60% humidity. I open my safes probably 1-2 x per week. I just cleaned all my firearms after 25 months of storage and found them all to be clean and rust free. Before storing, I wipe down each gun with RIG/Hopps oil mix, swab the bore with oil and place the gun back in the safe. I always handle guns with lint free cloth gloves and clean guns wearing gloves. In almost 30-years of storage I've never had a problem. Temp variation or high humidity is the killer. Keep 'em at a stable temp, keep 'em cleanclean and storage will not cause a problem.
To Ifacfp,
I don't know the right temperature but as I understand it the goal should be to have firearms kept at a stable temperature so that humidity cannot settle on the metal.
I remember reading a magazine that advised hunters who hunted in the wintertime to consider leaving their firearms outside in the cold so that moisture wouldn't condense on/in the barrels when they brought them inside, unless they were able to immediately deal with the condensation.
I believe humidity is the damaging factor, but am not knowledgeable on the technicality.
I am certain someone with more knowledge than I will answer better.
Regards,
Doug