An 8K is certainly a good shave and still has a bit of ability to cut. There are plenty of people that began touching up blades on the 12K Naniwa Super Stone and have had great success. Unless you start doing restoration work there is no point in going lower that the 3 or 4K that often come as part of a combo hone. If all you are doing is touching up you will likely never need less than an 8K but they are a handy combo hone. Natural hones are a bit of a rabbit hole and if you go down that path there are so many natural finishers and techniques for working with them I just have to say there are tons of threads to join in on.