Little story about WD40 and long term storage.... my aunt has a 1930's model Winchester pump .410 shotgun that was her late husbands. It has always been kept in a old fashoned gun sock with a zipper, looks like a alligator patern but is made of plyable plastic or something similar from back in the 70's.
It was put up in a closet where the hot water heater is, and forgotten. I got it out several decades ago, and it had a pretty good start of surface rust going. I got a sock and some WD 40 and gently rubbed it for several hours, and the rust was removed with some but not all of the bluing. Very little pitting thankfully.
I sprayed it down good with WD and put it back in the sock back in the closet with the water heater and promptly forgot about it.
Jump forward 10+ years, I rememberd it and thought aww crap its gonna be bad. Got the sock out, took the gun out and it looked just like when I had put it in the sock except that the WD was no longer "wet". No varnish, just a rust free gun.
It gets humid at times in Oklahoma, plus being in the closet with the hot water heater so I know the gun was subjected to moisture over the years.
That sold me on the stuff, have trusted it ever since.
Your results may vary but I have almost 40 weapons that are kept clean and rust free thanks to the stuff