Ever since I was a kid, I've had knives - and there was always a competion on who had the sharpest knife. The benchmark was shaving hairs off an arm. In other words, I've been sharpening stuff since I was a kid.
I also have a very old, small sharpening stone somewhere (I couldn't find it), which is cimpletely worn out with several deep grooves in it from sharpening hooks, knives and other pointy stuff (like spear heads and arrow heads).
I haven't used it for many years, since I got the set of Tiemco ceramic sharpening stones I use now (see pic). In fact, I think I have a total of four sets (one for the saltwater kit, one for the dry fly kit, one for the salmon/seatrout kit and one for the pike kit). I wouldn't be without them. I'm sure there are other good stones out there, but this combo saves most of my hooks after "incident", and I haven't really found any reason to look for others. I find most "diamond flies" are way too rough, but if you know of other good stones for hooks, let me know!
Modern hooks are deadly sharp, sharpened chemically and optimal right out of the box (most of them anyway). But even modern hooks can get dull, nicked or even bent. Bent is bad, and often impossible to rectify, but dull and nicked are easy to fix.
If a hook is "just" dull" and needs a touch-up, there's absolutely no reason to discard the hook and an expensive hook. A few strokes of the white ceramic stone's smooth side and it's back in business. If the point if nicked, the blue stone cuts more metal and is able to set a new point, and after a touch up with the white stone, any hook can be brought back to out-of-the-packet-sharpness.
Of course you can say that you don't care and simply change the fly, and that's cool with me, But I like to be able to touch up a dull point, and wouldn't be without my sharpening stones.
I keep them in a small zip lock back - otherwise especially the blue stone can eat its way out of the pocket. I'll make a leather holster for them one of these days.
Have a great weekend!