I keep my home at about 78 degrees and 70% humidity and have never had a rust problem or problems with wood. I clean and apply a light coat of lube after shooting or at least once every three months. I don't know if it is the perfect conditions, but it works for me.
Most wood stock material contain from 3 to 7% water. So I would try to control humidity to no more than 6 to 8 % if I didn't want the wood stocks absorbing moisture over a period of time. I have kept guns from 120 deg. F. down to 40 deg. with no apparent problem developing. While in Alaska, I tried to keep scopes out of very warm rooms after being outside all day in below freezing temps. Brand new scopes that still have the internal nitrogen intact could stand the change, but most of my scopes at that time were very time worn. ... Big Cholla
To summarize the old long thread, a stable temperature and humidity at 72 F & 50% would be fine but without large efficient AC hard to maintain.
So some of us suggested a lower setting on the dehumidifier to control for temperature swings, I keep mine set at 40 in the garage and 35 in the basement.
Roger