Just as a note for some of the new guys… I am seeing about 400 knives or so out of each set of stones before I consider them worn out. The 800/1k maybe sooner if I want good crisp apexes and no burr.
Curious to hear other’s thoughts too…
I suppose the best way to tell your stones are worn out is by their lack of performance? By that I mean they just stop working effectively on the blade. Correct?
You nailed the truth there ET! The cost of a set of stones is minimal compared to the cost of the equipment. I have no complaints about either I guess I have learned that buying the best is worth it in the long run.
Until I got my WE and started sharpening my knives, I did like most of my friends…made a terrible mess of blades trying to make them sharp. Once the guys I hunt with saw my WE sharpened knives, they started asking questions. I started sharpening theirs too, without charge of course. In the past month. I have sharpened over 50 knives for them. Believe me, some of them required major surgery! So, if I keep this up, my stones won’t last me a lifetime…I hope!
I enjoy it though and my buds appreciate it, so all is good.
I guess 400 is a good estimate. I’ve changed all of my stones once and the 800/1000 grit ones twice. But this includes the year I was sharpening for a restaurant and many times I just touched up their knives using the 800/1000 grit.
It also depends on what you do most. If you do a lot of work for others and you are reprofiling a lot, the 100 grit stones will probably suffer most. You indeed notice they get worn out by their lack of performance, Gary. The good news: my worn-out 100 grit stones have long lasted me as an alternative to my 200/400 grit stones 
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Josh, what type of knives are you sharpening (of your 400 per stone)? Quick sharpenings at the same angle, big re-profiles, touch ups?
I have noticed my 100’s are smoother than my 200’s. No surprise to me since I do a lot of re-proiling then just use the 200’s to get the scratches out. Since the 200’s feel rougher I spend more time with 400 and 600’s.
While we are on this topic has any one worn out strops? And cutting them to shreds doesn’t count.
All sorts of knives w/ different steel - high carbide and low. However, I will say that on a lot of what I sharpen I do the major reprofiling on a belt sander then just micro-bevel w/ my 800-1k stones, so they probably get used the most. But when I reprofile by hand (semi-frequent, always when doing a mirror edge pretty much) I start w/ the 100’s and work my way up.
I’ve gone through several strops… some because of them being nicked up, others (and more likely) is cross contamination. When I mirror an edge I can’t afford for there to be any contamination in any of the strops, so I have to change them out.
I for one may not be using the setup for business. What I have noticed after around 40 knives is that the stones are more smoother not as rough as it is new. Of course some stones are used more than others depending on what I needed. Hopefully these stones can last a lifetime. If it does then the cost of ownership is justified IMO. What I worry most is damaging the stones due to handling as the ceramic stones are fragile.
I love this quote! Never heard it before, but I will be using it, now. Hoping you don’t mind. Great quote.