I deal with old fractional HP fans and pump where the life must be extended beyond what you'd usually do when replacements are still available. Ages go from 15 to 30 years.
Around bronze and even steel sleeve bearings there's usually conical cup of sorts to hold the bearing and, originally in some motors a type of grease that over time dries up and leaves a brown powder that cannot be reconstituted, even with fresh oil. It looks like old sawdust and turns to powder when prodded at. I can pack oiled felt in place of this stuff, but what is this material? Is there something better than scraps of felt to keep those olive-shaped bearings oiled for as long as possible? The amount of wear they suffer by the time they cook out and seize up is not good, so they need even more oil than when they were new.