I have 4 keyboards with MX Browns. The oldest is a Filco Majestouch (original version), and is 3.5 years old now.
Over time, the touch has lightened up a bit. Not sure if it's the keys or my typing, but I feel the so called tactile feedback more, so bottom out the keys less often. I'd say it's just as solid as ever. When new, the larger keys squeaked, with back-space being the worst. The spacebar stopped squeaking by itself in a month or two. For back-space, a light coat of dry teflon spray lube fixed the squeaks.
At this point, I'd say the Filco and the Rosewill RK9000BR are tied for my favorite. For a while, the Rosewill was in the lead, mostly because of its crisper feel, but I think it has loosened up a bit over time. There's also a thread going here about minor surgeries to keep the Rosewill's alive, while my Filco has never had an issue.
Personally, I don't like the newer Filco's quite as much as the older ones. I have a Filco Ninja 10-keyless that I do no like near as much as older Majestouch or the Rosewills. But, time will tell, since the older Filco is getting better with age.
Edit: Just checked, it's 3 1/2 years old.