I have experience in knife sharpening. I would get to Dalstrong sharpening stones. You want one with a low Grit and one with a high grit.

Just do a bit of research. You also need an angle guide. It's a little piece of plastic that you use to angle the blade properly. If you're just sharpening the knife to use at home the sharpening blocks should last you a very long time.

It really depends on just how much you use it. I have less than five knives that I sharpen so mine will probably last me forever.

But it's a numbers game, because the more you use it the more it wears down. And it wearing down is inherent in the sharpening process. This is true for all sharpening stones.