According to the NRA:
50% humidity at 70 degrees is considered ideal "Arms Museum" storage conditions.
Any dryer then that, and you will have problems with wood stocks drying out and shrinking / checking.
Actually, if you don't have wide daily temperature swings in your house to cause condensation on the metal, whatever the humidity is, is probably just fine. (Unless you live on a sea-coast with salt-spray air.)
I have had a bunch of nice guns stored in cabinets without any humidity control here in Kansas for years without any rust problems at all.
In spring & fall, indoor humidity may reach 65-70% or more.
In winter, we run a furnace humidifier to raise the humidity in the house.
But my guns are wiped down with R.I.G. after every handling, and my home is heated and air conditioned mostly year around, at a constant temperature so condensation is just never going to happen.
In winter, when I bring a gun indoors, I just leave it out in open air with a ceiling fan running until it has reached room temperature, wipe it down with a Rig-Rag, and put it away.
I've never had a rusty gun in over 55 years of storing them this way!
rc