I know, I have a vibratory sieve at work that is around 20 years old, still using the original bearings. 10 years ago I just repacked them with molyslip grease, and it is keeping them cool and quiet. New bearings will be at the $500 mark, each, excluding taking a half ton motor to a machinist with a 10 ton press. So keeping the old ones running for as long as possible will be good. Luckily they only do 1440RPM, not the normal 20kRPM plus of a decent flywheel store.
I saw one where they ran it at synchronous speed of 1800RPM by making the motor the flywheel, and simply making it a 5 ton moving mass. They used massive double ball races to just handle the axial forces, the radial being done by roller bearings running in an oil bath each side. Generator side used a 3 phase excitation system that ran a rotating field around the rotor at double the slip rate when it was being used to deliver backup power, so that it delivered a constant frequency output even as it slowed. That used 5 slip rings and big brushes to handle the low frequency AC excitation to the rotor and the synchronous motor side.
Big, really heavy but it would provide power for the few seconds from mains fail to the time a big dry clutch would engage to start the even bigger diesel engine it was using as secondary power source. The engine was guaranteed to start, seeing as it had such a massive starter motor turning it. Oil pressure for all was provided by an electric gear pump, so the engine always had lube on all bearings. Otherwise that shock start would tear the crankshaft apart.
Electronics in it was almost nil, it used all contactors, magamps and RC delays. It was a pretty good room heater as well. And just for redundancy there were 5 more in the same bunker as well. Fuel for it could be best described as "adequate" in the old Rolls Royce fashion.