Some years ago I did give it a try at -80 C with polyester based B&W film. After defrosting slowly, 1 day at -40 C, 1 day at -20 C and 1 day at +4 C, the emulsion had signs of freezer burn at some places and cracks on other places. I didn't try other defrosting cycles.

I have no problems so far with film stored at -40 C but most of my film is stored at -20 C