The paint can tins are not reliably air-tight for long-term storage.
I know this because I've ordered inordinate amounts of
STG's "My Own Blend" selections from The Danish Pipe Shop over the years. MOB tins are the same as the HU tobacco tins.On re-check, some tins have stayed perfectly sealed, others not. Unopened tins seem to be ok, so I'm guessing that it's the opening/cosing cycle that messes up the seal.
Same goes for Mylar ziploc bags. I used to be a big proponent of Mylar ziplocs for long-term storage, but it seems that the weak link is the zip seal itself. The bags are great for short-medium length storage, though, and
I'm loving the tin-sized bags. Perfect for keeping your current rotation, in the tin, from drying out. If you have a vacuum sealer that will do Mylar, then the heavy weight (4 mils on up, like the Germain bags) bags are a good long-term storage solution. Tale note that the
FoodSaver (channel type) vacuum bags are not Mylar, are oxygen permeable and are not acceptable for long-term storage.
So, these days, I either stick with Ball jars or I vacuum-seal into
heavy Mylar bags.
Throw in an O2 absorber and get anaerobic fast!