If they aren't like 20+ years old and as long as you don't try to take the liners out of a really low volume boot when they've spent all day in -10F weather there isn't much risk of cracking.
I cracked the cuff of my Salomon Quest 120 boots at the pivot because I tried to take out the liners when they were really cold. Luckily they were still under warranty and I think it was a fluke. But I did have to ski the next day with like 3 titan straps around the cuff and instep. I ended up upgrading to the Quest Max 130 because Salomon was awesome with the warranty process and just gave my bootfitter money and then I went and found a shop that had them in stock during the 1 week window I could see the fitter