Personally, you could do without the 12000 the 8000 is a good polish for the edge and anything higher only refines it a bit, anything much lower and it starts to feel harsh. I like a finishing step after the 8000 but there are about a dozen different pastes, hones, other abrasive substances to try so I like to keep my finishing options open.

I guess what I mean is that every razor I have needs at least an 8000 grit step to be sharp but when going finer than that there is a lot of variation in what seems to be the best final finish for my razors, some like nothing, some like paste, some like a fine barbers hone, etc.