Originally Posted by
Slaninar
External bearing BBs - Shimano Hollowtech, and the rest - with, or without frame threading, do last a lot shorter than the older, which had bearings inside the frame BB bracket (square tapper, and Octalink 2). They start making noise rather quickly.
+1
In my experience, the internal cartridge bearings last about a decade, (Shimano and Campagnolo).
I've had external bearings start making noise in as soon as a year (Shimano).
(I ride ~4000-5000 miles/year, with most miles on just 2 of my 4 bikes.)