Mine aren't vacuum-tight, but I've got malts that have been in there for years without any perceptable change (I bought 5# of black patent malt once - derp - that will last a while
).
Even people that use airtight containers can have a problem. Grain weevil eggs come with the grain - a trojan horse present for you. So, it's possible to open a sealed container to find these guys. Ironically, while slightly disturbing, had no effect on the malt (wife was a different story).
Even people that use airtight containers can have a problem. Grain weevil eggs come with the grain - a trojan horse present for you. So, it's possible to open a sealed container to find these guys. Ironically, while slightly disturbing, had no effect on the malt (wife was a different story).
For those that are vacuum sealing and gamma locking I would think almost forever. I'm a roll the sack closed type and don't have issues lol.