The typical 24 hour cryo process seems to work well for audio items, which are placed into the cryo cooler along with non-audio items like gun barrels, golf clubs, engine parts, or whatever. I suspect the typical cryo treatment at a cryo lab comprises 10 hour ramp down, 4 hour dwell and 10 hour ramp up. These times could vary depending on size and density of the items being cryo'd. CDs for example reach cryo temps much faster than say a trransformer or gun barrel or French horn.
I would be remiss if I didn't mention freezing audio items in the home freezer, which is also an irreversible process and provides very good results without all the issues related to shipping costs, down time, or temperature shock resulting from cryo temperatures. Cables and CDs, LPs, tubes, even CD players can be frozen overnight then slow thawed in the main refrigerator section for 4 hours or so. Voila!
If you try freezing CDs at home here's a little tip. After freezing and thawing the CDs wipe the data surface with a clean cloth or soft tissue as the freezing process, like the cryo process, drives a little residual mold release compound to the surface of the disc. Use the breathe test to make sure the CD surface is clean before playing.