Pellet lube and preservatives

There is no right or wrong answer regarding what to use. Any light oil- or wax-based substance will inhibit oxidation, and then the trick to not adversely affecting accuracy is to use only a very small amount. Enough to coat the surface but not so much that it pools to the inside corners of the skirt, and not so much that it produces a mist that gradually gunks up whatever shroud or LDC is fitted. 

FWIW, I gravitated to the bicycle chain wax approach (White Lightning or Krytech). Only 10 drops for a 500ct tin of .177 or about 15 drops for .22. Most of that volume is a carrier solvent that evaporates. It leaves a dry surface that doesn’t attract grit and doesn’t get my fingertips greasy.
 
I have used beeswax furniture polish ( with real beeswax) for over 30 years, no buildup, cleans itself, no sticky residue on your fingers, no nasty smell, good for the enviornment, keeps barrel clean and easy to clean, keeps pellets from oxidising. I have CP 7.9 from 15 years back that look like new. Also excellent for your nice wood stock and will seal it from moisture! 
 
I'm considering trying this with a product called "One Shot". It is a non petroleum wax, in an aresol spray can, originally used for case lubrication for reloading. Spray it on, it'll be dry in about a minute, and you're left with a dry, lightly wax coated surface. Made by Hornady.

I knocked a new tin of pellets off the bench in my barn. The floor is dirts. So I picked up the pellets. Blew them off with compressed air washed them then blew the water off. The next day after they were for sure dry I sprayed them with "Hornady One Shot" they shot awful! They were JSB Exacts that I shot out of my 177 Huntsman. 
 
A time tested lube for PCP is One Lube by Slick50. Field Target shooters have done the research, it works great. I started using it in 1997.

I believe most people tend to use a lubricant to enhance accuracy not so much to keep the pellets from going bad. Alan Zasandy, who built and tuned a couple of my long distance PCP’s for me, uses Slick 50 so I use that for those guns. My other guns shoot great without any lube but they are all used for non competative 60yds and less. I personally won't mess with a great shooting gun. Been there... done that.

You might want to find another place to store your pellets and/or use dessiccant packets. I have about 20 opened tins, which some are 15 years old, used for testing new guns. I have never seen any tarnish and none are lubed.