Use caution when greasing up your firearms for storage. The problem is that grease can trap moisture underneath it. Cosmolene goes on very thin and will penetrate/cover all surfaces. Then it thickens into the slime that we all know and love. Cosmolene will actually displace moisture as it's being applied. You can get a gallon of it for less than a hundred $.
If you store your firearms with any kind of "slime" on them, be sure to store a few supplies with them for cleaning them up at a later date. (Rags, Mineral Spirits, bore brush, etc)
Personally, if I needed to store firearms long term, I would use a different method. After a good cleaning and lube, I would vacum seal them inside a couple of heavy plastic bags and then put them in a case. Use a bore dessicant tube (
http://www.barrelguard.com/ ) and another 1/4 pound of dessicant in the bag with each one. If you wanted to go really crazy, seal each bagged firearm in a PVC tube filled with nitrogen. You could bury that and it would be fine for a few hundred years! Keep yer powder dry, Mac.
Tuff-Gun Finishes. The Name Says It All.
Mac's Shootin' Irons
http://www.shootiniron.com