I sharpen mine about once a month. I am on the ice a lot over the course of a week though; I skate about 4 times a week at about 2 hours per session and teach LTS twice a week. The rule of thumb says to sharpen them about every 20 hours or so of skating time, however this can vary depending upon the condition of the ice, your level, whether your skating outside vs. indoors, etc. I can usually tell its time for a sharpening when my spins just don't hook well; you can usually feel your edges aren't grabbing the ice well.