What exactly is decanting…what are the advantages and how do you do it properly?
Decanting(as referred to snuff) is moving it from one container to another. Generally for longer term storage to maintain freshness. I use ball canning jars mostly, and follow general canning methods for sterilization. Use a spoon for actual handling of the snuff in between containers and from there to your snuff box for minimal exposure of your snuff to outside influences. Snuffs(particularly the drier ones) will stay quite fresh for long periods if properly handled.
Also moister snuffs have the ability to corrode metal (esp aluminium) tins which ruins the snuff and probably not a great idea to insnuffalate little metal bits.
Canning jars. Sterilized. Clean implements. Dark and cool storage area. It will last for years. I’m not sure it “ages” like some very good Virginia pipe weeds do, especially flakes, but I’ve got a stash of Cafe Royale thats pretty damned old and pretty damned good. YMMV