Just like hay they are good until they go stale or moldy. Just check them over to make sure they still smell good and not moldy or dusty smelling. I think cubes actually last longer they loose because it's compressed. Pretty much the chins will tell you before you even notice when they are no good, they will stop eating them. I bought a big bag of alfalfa hay cubes from the feed store over a year ago (it was only about $10 so I didn't realize how huge the bag was until my husband brought it home, lol), I just keep them in a bin and the chins are still happily munching on them when I give them some.