My fronts (129 SL) were repacked last week after 19 years and 106k miles on the original green MB grease, which, on the inside of the cap, looked like dried candlewax that had been stuck in the freezer! There was some scoring on the spindle, and some gray ooze of metal shavings deep inside mixed with the remaining "fluid" grease. They were a little loose, and I can tell a difference for sure.
I've found that front shimmy can often be caused by even slightly-loose bearings. On my 124, it was suggested to check pretty much everything plus the kitchen sink (factory part of course
), however the shimmy never went away until the bearings were repacked. It should be a required service after 100k.
What are the symptoms of rear bearing failure? I do have a mystery "hiss" on my car, that is only audible when cruising with the top down at hwy speeds, when I go under a bridge or up beside a wall. As in, the sounds my car is making are then echoed back toward the cockpit. It isn't audible under the hood at idle (pulley, etc) nor during top-up or low-speed driving.