I have an important warning about Kodak's liquid fixer concentrate and cold temperatures. For a time I had my photo chem in a backyard shed with no climate control. It dipped into the 40s for around two weeks. The next time I checked the chem the fixer was destroyed. (The developers were all fine.) A thick sludge precipitated out of solution and it looked so funky I wasn't confident about using it again. I tried stirring up the sediment but it didn't remix. The concentrated fixer was unmixed and uncontaminated since I don't dilute it for use all at once.

So while temp doesn't drastically affect fixing times, be careful about cold storage conditions.

(I'm not a chemist and I don't even play one on the internet. I've done BW constantly since the 90s and I'm generally pretty careful with my process. It's the only time something like that has ever gone horribly wrong for me.)