When I do my own cable and layered damascus, I double temper then cryo then temper one more time. Most of the time I have 5 or 6 blades together and when cryoed do it for at least 6 hours and most of the time I put them in in the evening and return the next morning to get them out. I use a friendly farmers semen tank of liquid nirtrogen suspend them with stainless welding rod thru holes in the tang and suspend them slowlyuntil submerged. On my stock removal blades of D2 and ATS 34 I cryo them after they come back from a commercial heat treater and then temper them at 300 degrees for two hours. I have taken several of my knife store friends blades from commercial knives out and simply submerged them for the time period and they are amazed on the increased edge retention even if the factory says they are cryoed. I wonder then about the length of time they do them. For me at least 6 hours on everything and most end up 12 hours AND I FIRMLY BELIEVE IT HELPS. Mike