I have only been using my OM since I got it (Feb 1st) and have noticed the spin time dropping off significantly (down to 2 minutes) in the last few days. I thought it may be the new cheap all-ceramic bearing failing but on closer inspection of the grinder I can see a line of resin forming on the bottom plate, I noticed the new design has dropped the diamond tipped inner row of teeth for flat like the others that caused the smear in the pic,
I used my S&B brush as the post for the top plate to check the bearing spin time and it is the same as when I got it, just over 3 minutes so it is the build-up that is slowing it down.
So I ended up just iso q-tipping the tips of the top plate row of teeth that made the smear on the lower part and have been spinning the heck out of my OM and only grinding a smaller amount each time instead of loading up as much as possible in the grinding area. The smear mark has now disappeared and my bearing is now spinning for over 3.5 minutes, ceramic bearings are 'self healing' so can take a little time to bed in and work like glass on glass slippery without lube!
I found the seller I got my ceramic bearing has the same full ceramic bearing but in a higher spec, Abec-9, the one I have is Abec-7, this refers to the tolerances of the build of the bearing, Abec-11 seems the highest available. Anyway, still cheap at AU$7.80/US$5 and fixes the 'hard to remove top' problem,