After half a dozen years, the bearings in the blender impeller felt pretty bad:
I wiped everything clean, found the box containing the box containing the tube of bearings, packed the base with more silicone grease, reassembled everything in reverse order, and it’s all good again.
The first repair lasted for a year and the second for six, so I think overpacking the base with grease helped a lot. Maybe I’m getting better at ignoring horrible grinding sounds.
I can do this twice more, although the Jesus clip holding the shaft into the bearing stack definitely needs replacing.