Just as a follow up to this post......

The "noise" I started hearing at the 60 hour mark with my printer seems to have been fully resolved with lubrication. I haven't heard the noise since.
From now on, ever 25 hours I'll lubricate the rails.

I can't speak for anyone else, but considering the stresses on the moving parts of a 3D printer, I would STRONGLY suggest adding periodic lubrication to the rails in order to make your printer last. Dry friction is not a good thing.

Of course printers are different and YMMV