I have used it a couple years later. But not if it has been in and out of the freezer a lot. I think that freezing and thawing would degrade it. I have a lot of contact lens cases... Several hundred... So if I think I will use a lot if pollen, I will freeze several smaller batches and not put it all in one. That way I am not thawing and freezing all my supply every time I want to use any of it.
