Let me preface this post by saying I do not like the sound of typical flatwounds after they "break in" (go dead) to what most players call "thump," or the brands that actually come that way new (I recently got a bass that had a new set of Labella flats and was shocked at how much I didn't like the sound--they came off immediately and got traded away). So, I recently got another JMJ Mustang (new) with the stock Fender flats. My previous JMJ, I changed to rounds before I even got a chance to hear the flats. This time I left the flats on and I must say, I'm very happy with the sound so far. They are very nearly as bright and lively as the only other brand of flatwound that I actually kinda like--Ernie Ball Slinky Cobalt Flats. In fact, in a certain respect, I think they ARE as bright (at least for certain frequencies in the sound). And the Fender flats actually feel better to me; they are smoother and slicker. I think the sound has a bit more body and "growl" as well. Also, every set of cobalt flats I've had has come with a somewhat dead A string. I guess it's just the way they are for some reason (I've had probably ten sets). That's not the case with the Fender flats. They all sound nice and bright (for a flatwound) and are very even across the spectrum. What is most pleasing to me is that they are the ONLY set of flatwounds I've ever had that I actually like the sound when thumped/slapped. Most all flats I've tried (including the cobalts) blast like hell (enough to take the top of my head off) when slapped with a godawful midrange bark that is extremely hard to keep even in level with fingered notes, without heavy limiting/compression. That's not the case with the Fender flats. I can go from fingered basslines to pop and slap with minimal level change. I can actually dig in with the Fender flats and it sounds good all across the spectrum and with all the various styles (fingers, slap/thumb, pick, tapping, etc) and doesn't get such an "in-your-face midrange howl" as other flats seem to do. Chordal playing comes off nicely and is, surprisingly, not mud soup--very articulate for flats, without any string noise whatsoever. Nice. Overall, I think I'm more fond of the Fender flats than I am cobalt flats. They really are pretty much just as lively, defined, more even in output, and as bright in certain respects, at about half the price. So I think this bass will stay strung with Fender flats... and maybe a couple more will join it. So.... HERE is the question: how long will they stay that way??? I have a couple of weeks on them right now and they haven't noticeably lost their brightness. I want them to stay that way. How long can I expect them to live up to my expectations?