So what is the benefit of these tubes? Is it a night and day experience? So it sounds like I have to wait 500 hours for them to sound their best? Some styluses do not last that long.
The short answer is yes, it can be anywhere from a very noticeable difference to a night and day experience, depending on which you use and how it meshes with your equipment (and the quality of the equipment and your ears). Think of the fuse as an extension of the power cord. If you accept that power cords make a difference in SQ, then the design of the fuse follows as well. I started with fuses several years ago on the lower cost end, HiFi Supreme and Furutech, which are very decent, and eventually worked my way up in SQ and price to the SR and Audio Magic.
As an example, in post 827 I mentioned how the SR Blue didn't cut it for me, despite the accolades it was getting from lots of people. In fact, I felt like tossing my system out the window with the Blue because of the coolness it brought to the system. I switched to the Audio Magic Ultimate fuse and that worked much better. Now I have the newer SR Orange in a few locations (+ AMs in my active speakers). With the Orange's much needed new warmth it now sounds a little better than the Ultimate (don't know about the Ultimate Premier because the one I got fell apart on me, which is looking to be the topic of another post).
I suggest picking one fuse in your price bracket (check the pro & user reviews) and try it in a key place, e.g., preamp or amp (if you get an SR, go a little higher on the amperage, e.g., 1.25A or 1.6A instead of 1A, because they have been known to blow at the spec'd level). And unless you find a really good used deal, buy through a shop, such as Highend Electronics, which offers a 30-day return. A fuse should be listened to in both directions, as one way usually sounds better than the other, and sometimes in the opposite direction a company specifies, if they happen to (generally current comes into the fuse left to right, and the direction of the fuse's lettering is a good direction to start). Usually 300-400 hrs is enough burn in to have a good sense. But remember, if power to the unit is always on, and even better if the unit keeps a small voltage running as so many do, then the fuse is being burned in 24/7. Hope that helps,