I just replaced four of the five bearings in my 360 horizontal stab a few weeks ago.  With almost 900 hours, I noticed some vertical play in one outboard bearing.  The bearing blocks were fine.  The outer edge of the race had worn the ball.  The bearings were COM series, which is at the bottom end of the quality spectrum.  (The same series is used in all the landing gear components, as well).  I have been replacing all of these with higher grade bearings made of heat treated alloy steals and with more than twice the load rating.  This extra margin slows wear tremendously.
  
Chris Zavatson
N91CZ
L360std

Christopher Zavatson
Mobility Technologies
United Defense
(408)289-4329