I put large amounts of open snuffs in glass mason jars, and I have some in little plastic pill boxes.  I’ve had some for coming up on 2 years now and they’re fine.  I think there’s a hint of plastic smell in some of the pill case ones, but they’re still fine as far as flavor and moistness.  I have some tins I keep in heavy duty ziplock bags when not in use as well.

They are stored in a cool dark basement if that matters.

I bought a lot of large amounts when I started because I’m just like that.

I keep half a year’s worth of snus in my basement freezer at any given time too.