You shouldn’t use this stone often, as it will wear your knife down. The #2000 and #3000 grit stones can be used more often if you are the sort of person who likes to sharpen a bit more regularly as they are less coarse, but again, they are designed for sharpening and not maintaining your edge.Once you get into a routine, you will get to know how often you need to use your medium stone.
To take off the fine scratches and the burr left by coarser stones, and polish the surface, one can use stones starting around 2000 grain. Above that there is theoretically no upper limit, but at the same time stones above about #10000 provide no measurable practical improvement in the edge. It is also interesting to note that above #8000 grit, there is no Japanese measurement standard. With all the stones labelled as having a finer grit, one simply has to take the manufacturer’s word for it.