After a few years, I would replace any kind of sharpening stone. If you run your finger across and feel any grooves or just can’t feel any coarseness, it’s time to replace. I mention the grooves because I just feel grooves can harbor bacteria (I’ve not seen any studies on this though). Also, if you feel your instruments aren’t getting sharp by checking on a plastic stick, but then after using a different stone the instrument is sharpened, its time to replace. It is dependent on how much you sharpen, but the point is, they don’t last forever! You may want to contact the manufacturer on how to properly clean it. I hope this helps!
Thank you. Ive already gotten rid of my flat stone. Maybe its time to replace this one also.
shelly mcmanus