I have used B&W film that was frozen for 20 years and it had no fog. Stuff that was opened, and then frozen, has typically had about 1/2-inch of fog at the opened end. Other than that, nothing. I suspect that film fogging is actually due to local radiation, so it varies with your location.
If you are talking about B&W then fog is really not an issue. You can just print through the fog.
Loss of contrast is a bigger issue but again with B&W it is easy to adjust for as long as you have several rolls of film from the same batch. Once you know how to develop one roll you can use the same method for the other rolls in the batch.
The real issue is fade of color dyes and the fact they fade at different rates. Low temperature will slow down the fade of these dyes.
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