Got a call from Gabriel Devault, inventor of the Zaero redrive. During and after the discussion, the following points were revealed:

Bearing maintenance
Q: How long do the bearings last?
A: Three answers:
1. Recommended replacement of Zaero and motor bearings at 1000 hours.
2. Preflight and annual / 100 hour inspection item: Listen and feel for growling or other unusual noises like high and low frequently rumblings or thumping from redrive system including two redrive bearings and Zero motorcycle motor bearings.
3. The SKF bearings used in Zaero and motor are identical. A bearing calculators was used to validate loads in this application. See photo below of a calculator.
The Zero motor controller monitors temperature and displays warnings to pilot. For the Zaero I suggested pointing an infrared temperature sensor at the hub housing the two bearings and displaying to pilot in flight.