I am always on the lookout for project guns and will often end up with them sitting in my shop for several years before I can get to them. Often I will apply RIG on one that I have not cleaned and have had no problems with rust(as long as visitors do not pick them up and wipe off the grease). It is inexpensive, quick to apply, and last nearly as long as cosmolene(and you don't have to take your gun into the shower to clean it with a red faced DI screaming in your ear). One thing I HAVE HAD A PROBLEM WITH is heat affecting the wood, especialy if the stock has oil in it and I have not degreased it. I live in a humid oven of a location so that adds to the problems. Something you may wish to consider is purchasing an umbrella insurance bond that will cover theft, fire or AoG.
Shoot safe but shoot often,
Vic Shultz