A: When it comes to the best knife sharpeners used in a domestic setting the abrasives used to sharpen the blade should last for quite a few years. When they do eventually wear out many of the best manufacturers will refurbish them for you, typically for a nominal fee. Again, however, unless you are using the sharpener on a daily basis (and there is virtually no reason the average person would do this), the sharpener should last for many years before ever needing service.
Whichever method you choose, be it a waterstone (also known as a whetstone), or a pull-through (either V-shaped or ceramic wheels) it's important to regularly hone your knife with a honing steel, which we'll also cover below. You'll be pleased to hear that you won't have to reach for the stones too regularly – once every two or three months should suffice. 
Medium Grit Stones: The number range here is from 1000 to 3000, with the latter being the basic, go-to sharpening stone. If your knives have lost their edge and need a good sharpen, then this is the grit you should start with. Don’t use it too often or the knife wears down rapidly. If you like to sharpen regularly, then the 2000 and 3000 grit are the ideal choice as they are less coarse, but please remember they are designed for sharpening and not maintaining the edge.
In addition, the most prized of the natural Japanese Water Stones are quarried in the Narutaki District north of Kyoto, Japan and are commonly available as either bench stones or pocket stones in grits ranging from 120 to 12,000. On the other hand, synthetic water stones are made from Aluminum Oxide and commonly available as either bench stones or pocket stones as well in grits ranging from 220 to 8,000 and, although this is the same abrasive material used to make India Oil Stones, the difference between the two is that the binder that holds the abrasive together enables Water Stones to be much softer than India Oil Stones which, in turn, promotes faster cutting because the worn abrasive material breaks away more quickly and is replaced with fresh, sharp, abrasive material more quickly. In addition, because water stones do not become glazed or loaded with swarf like oil stones can, new abrasive particles are constantly exposed as the stone wears so it continues to cut consistently. Plus, they can be lubricated effectively with water (rather than oil which can ruin some water stones) which combines with the fine particles of abrasive from the surface of the stone to form a slurry which polishes the bevel as the stone cuts. However, it should also be noted that Water Stones do become uneven significantly faster than other types of whetstones although, their softness does make them easier to true again.
I've always wanted to sharpen knives on water stones, and this set gave me the motivation to finally give it a shot. The price is amazing for the quality and content of the set. It comes with all the grits you need to sharpen anything... I usually start on the 400 grit if the knife is very dull, or directly on the 1000 grit if it's not too dull. The 3000 and 8000 grit stones are softer and ideal after the coarser stones. The online learning section is truly amazing, much better than I expected. A convenient place with instructional videos and many articles about knife sharpening. Only downside is that the knives are now so sharp I need to be very careful using them... but that's a good thing! I feel like I fell in love with knife sharpening again.
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.