You shouldnt freeze freash shrooms put them in he fridge in a paper bag an they will keep for at lil less then a week ...but when there dried they can stay there for months i have heard years as well just never have them long enough
Once your shrooms are completely dried out you can wrap them up real good and store them in the freezer for up to a year I believe? After so long tho they start to loose their potency.
And yes, NEVER freeze them when they are fresh, because when thawed they will turn to slop.