Yeah, age of the beans can catch up with you. Storage method can also be a culprit. E.g. storing greens in a cloth bag is about like leaving the beans in an open tray- keeps the dust off but little else. Some plastic bags are sufficiently ‘porous’ that they allow water molecules to escape and the beans to dry.
I imagine the best choice is a metal or ceramic container with a seal in the lid but that’s more weight than I want to deal with. So I use a thick-walled Tupperware-like plastic containers (each lid has 4 latches) and have no clue how porous the walls are. I go thru about 50# in 3 months with greens divided among 7 containers with 7+ lbs each. So far it seems to work but hardly a recommended approach- especially if the storage time is substantial.
Bruce