O-1 was specifically designed for high hardness abrasion resistant applications, so its “sweet spot” for hardness to toughness ratio is actually up around 61-63 HRC, to bring it softer is fine but it would probably be more effective to switch to another alloy that would have its toughness peak at a lower hardness level.
The cryo debate will rage on for the foreseeable future, and all we have to go on are the verifiable facts that can be entirely explained at this time. Among these are that one should not see a noticeable jump in HRC from freezing simple alloys (O-1 being one of them), and if you do, the easiest way to fix it is to just lower your hardening soak temperature to avoid the unnecessary retained austenite. The other verifiable fact is that the VAST majority of papers, studies and findings on the benefits of cryo have been provided by folks who sell cryo services and thus it is portrayed as a panacea capable of everything from improving trombone sounds to women’s stockings. I take everything written on the topic with a huge grain of salt and suggest others to do the same.
Heavily alloyed stainless steels do indeed benefit from cold treatments since the chemistry makes retained austenite unavoidable. But simple tool steels are not in the same category and I feel safe in saying that increases in basic Rockwell in these steels are symptomatic of less than adequate controls in the hardening operation. There may be crystalline lattice “things” occurring with deep cryo that I keep an open mind about, but this is in the purview of serious cold, as in liquid nitrogen cold, and not just dry ice or the freezer.
Tempering for 2 hours 3 times (for a total of six hours) is gross overkill. Save on your time, and electricity bill, by at least limiting each cycle to 1 hour. Multiple cycles are good but much more than 2 hours total has little value in the long run.
Just about any oil will work for O-1 and the real fast stuff is overkill, if vegetable oils are your thing perhaps peanut oil instead of canola. If you do not get much bend before the blade breaks- congratulations! You have a fully hardened blade and not a ductile blade like object, celebrate your success and be happy, while ignoring the blade benders! For what it is worth how many springs or pry-bars has anybody seen that bent like a noodle? If you want to protect the blade from the point abusing joint splitters, the secret is in increasing the materials thickness and not compromising the heat treatment.