Depends on how you store them, how they were dried, and if they were dried. Fresh mushes need to be dessicant dried. If they are already dried properly, keep them dry and cold in a dark place, they can keep for years. I personally dessicant dry them, seal them in jars, and put co2 in the jars. Then I keep them in my closet like that, they have stayed good for as long as I have kept them.
Stick them in a freezer bag, get one of those keyboard duster things, stick the nozzle in the corner of the bag and fill it up, push all the air out then fill it up again and completely seal it, double bag it and fill the other one up to. Then stick them in the refridgerator. Will last awhile.
