It depends on the stones in my experience. Most of my waterstones need flattening after a couple of sharpenings, they get concave real quick. Not all of them though. I have a 320 stone that pretty much stays flat, also an piece of natural stone called 'Begian Blue' keeps its shape longer that most other synthetic stones I have. Reason for me to try some diamond stones and see how they hold up. Harder/tougher steels are another reason to try this out.
I draw a grid with a pencil on the surface after use, and grind it all away. I suspect the faster the stone, the more it wears. The middle of the stone wears pretty quick. A "Belgium blue" might be a coticule just like the back side of one. They are pretty slow in my experience.
Ended up spending probably way too much time researching these stupid stones lol, got one shapton professional 120 grit a suehiro cerax in 320 grit and a suehiro cerax 1000/3000 grit combo stone. Also got a flexxx outlaw paddle strop. I haven’t gotten my suehiro stones yet but the Shapton showed up yesterday and the strop today. Last night i reprofiled 3 ancient Chicago cutlery kitchen knives for my mother in law. They were terrible, she has a pull through ceramic sharpener and the bevel was completely gone from one knife! So dull I have no idea how it cut anything. So far the 120 grit stone did an excellent job reprofiling all 3. Now Just waiting to get my finer stones to finish! So far im really enjoying freehand sharpening!
Once you've got the hang of it freehand sharpening is the way to go. You can make some amazing edges. It's also very relaxing I find.
I absolutely agree, now that I’m actually able to remove metal at a good pace it’s very satisfying. I was getting a bit frustrated with my sharpmaker, not that it was bad or anything. It’s a great tool. Just not the right tool to fix bevels or Work down badly abused and chipped up knives.
I use a set of DMT diamond bench stones and a Lansky turnbox ceramic crock stick set to finish and maintain all my knives. This combination has been stellar for Esee and TOPS' 1095, Buck's high carbon stainless steel and Benchmade's D2. I like DMT's diamond stones because they damn near last forever and require zero maintenance other than washing them after use. I completely agree with Nathan, once you get the hang of freehand sharpening it's super easy.
DMT is the best there is when it comes to diamonds. Monochrystalline as opposed to other brands' polychrystalline matrix.
I am a firm believer in not letting my knives get dull. I have gone several years without sharpening a lot of my knives. After use, I give a knife a few strokes on a sharpening steel to get the edge hair popping again. I have a larger steel or two at the house, and keep a little mini one on my person or in my pack: https://www.eggintongroup.co.uk/brands/egginton/sharpening-steels/miniature-sharpening-steel.html