Just in case anyone else was wondering, I got a reply back from the manufacturer:
I've had customers freeze, but I'm pretty certain simple refrigeration is the safest bet. It keeps really well. Had a customer report year old stuff, not even refrigerated to be just fine. I'm not sure how freezing might, or might not affect the alkaloids. I wouldn't freeze, but I do remember someone on the forum mentioning that they did.
So I guess I'll refrigerate rather than freeze.