IMO, these are niche steels that don't have any reasonable real-world use cases and they don't need replacing. Sort of like having a special Corvette that only comes out of the garage for an occasional Sunday drive around town. It's not really useful (other than for collecting).
S90V, S110V have great edge retention and decent toughness and there's lots of models to select from. If you think you really need a knife with better edge retention than S90V, I would suggest you buy a utility knife with switchable blades.
These steels are too hard to machine and process, too hard to sharpen, too brittle for many tasks, too expensive... good riddance IMO.
I had only even heard of two of the three steels mentioned in the OP, and have never owned any knives made in any of them. But I assume, from the context of the rest of the conversation so far, that is most likely because I buy mostly hand made fixed blade knives that are not made on CNC equipment, and not many handmade knife makers would like working with steels that are this hard to work with.
So, I'm following this thread mostly to learn about steals I had never heard of yet that are being retired. As most of my favorite knives I carry are either CPM154, ATS34, S35VN, and S45VN for stainless, and A2 Tool steel, O1 Tool steel, 52100, 5160, 1095CV, and SK5 for carbon.
I've had one production knife in 20CV, one in S110V, a few in M4, a few in CPM Cruwear, and several in S90V, and while the knives themselves were fine in most cases, the steels themselves never reached star status or became hated in my head. I like my ZT 0350 TS in S30V more than I liked the ZT 308 TS in 20CV I had, but that is due to the size factor not the steel.
I'm curious to hear more about the steels in the OP, and what their attributes and shortcomings were for the people more familiar with them, for future purchases on the secondary market.
