A: That depends almost entirely on how often you use them. If you are a professional chef who uses his or her knives every day then you should hone them every time you use your knives. But honing has its limits and over time your edge is going to become dull no matter what. Therefore your knives will need to be sharpened at least several times a year. Some chefs, in fact, will use a whetstone on an almost daily basis in order to ensure their knives are always razor sharp. Most of us, however, are not professional chefs and may not even touch our kitchen knives for days at a time. In that case, it’s probably a good idea to hone the edge after every couple of uses and have your knives sharpened once a year.
There is no dominant standard for the relationship between "grit size" and particle diameter. Part of the difficulty is that "grit size" is used to refer to the smoothness of the finish produced by a sharpening stone, and not just the actual size of the grit particles. Other factors apart from particle diameter that affect the finish (and thus the "grit size" rating) are:
An important but often confusing area of sharpening is knowing when you're done with one stone and ready for the next finer grit. On coarse stones it is very easy. When you sharpen one side you will notice a burr forming on the opposite side of the edge. This burr is hard to see but is easy to feel. Very carefully feel for the burr by gently running your hand from the spine to the edge. (Do not run your finger along the knife edge from heel to tip, that's only asking for trouble!) A burr is formed when your stone removes material directly at the edge. The burr will move from one side of your knife to another as you alternate sharpening sides. Make sure you have felt the burr jump between both sides before you move on to the next finer stone. That will ensure that you have sharpened both sides effectively. The finer grits are done the same way but the burr is much smaller. On the finest grits you may not be able to notice the burr at all. Testing the knife sharpness will tell you when you're done. (Learn how you can test to see if your knife is sharp.)
Our large selection of stones from many well-known manufacturers will allow connoisseurs to find the ideal stone for their needs. Because all manufacturers formulate their stones to emphasize a different mix of qualities, and because these qualities can vary widely between different stones, most woodworkers choose stones from several manufacturers to build up an optimal set of sharpening stones. Then again, once you get to know the characteristics of certain types of stone, you may find one supplier who will provide all the stones you need. Sometimes this can be an advantage. But there is no one size that fits all; each stone must fit your needs and work style.