I wax the handguns I don't shoot. The Smithsonian and Royal British museums use Renaissance Wax to protect their historic firearms, so I do too. I've only been the curator of my colection for about twenty years, and I've only used the Renaissance Wax for a couple of years, but it seems to work as good as RIG. There are a significant number of dead relatives looking over my shoulder, and I'm sure Uncle Eldred, at least, would start haunting me if I did something wrong... Makes 'em real shiny too! Even so, I do a complete inspection once a year.
I've heard some people have used heavy auto grease for long term storage with good results as a cheaper alternative, and I once unpacked a vacuume sealed, 30 y/o, Chinese AK47 that was slathered in some kind of thick fish oil that smelled like the waste shoot at a tuna cannery. Seriously, my partner was dry heaving about ten seconds after we cut the plastic, and we carried it outside like it was HASMAT (it was). There wasn't a freckle on the rifle. It could have just come off a lathe (or a stamp press, or whatever).