I have been promoting this in self defense classes for years.
As has been mentioned, the bathroom is one of the places in your home you are most vunerable.
We keep old Md10 S&W. Police trade ins in each of our bathrooms.
Never had a problem with moisture. Here in Maine we do not have a high humidity climate, and I don't take the Smith into the tub rubber ducky hunting!!
In our case the guns are kept in tall bathroom closets or vanity drawers.
In a prior house I hung a Enfield revolver on a cup hook located inside the pipe chase for the shower.
Also we have no little kids left at home...