Will the stone eventually wear back down to 220 grit the more you sharpen?
That depends on what you are sharpening. With straight edge tools, the stone will stay fine until you use the other side of the grader and rough it back up. With shaped tools, like gouges and bullnose scrapers, you will eventually wear through the polished surface, exposing coarse abrasive grains. Use a light touch when refining the grind on shaped tools.