Predictive maintenance can be Vibration Analysis, Ultrasonic Analysis, MCA and Thermography.
Good Practice would be Acoustic Bearing Lubrication (greasing), Proper shaft alignment for shaft coupled installations, proper pulley alignment and belt tension for belt coupled installations.
Trimming keyway keys to the proper length and checking balance after install. Tropical environments, may recommend heaters if they are shut off for any length of time. Also can specify epoxy sealed windings for tropical environments.
Considerations in storing larger spare motors 10 hp plus should keep them in a dry, clean, vibration free place and rotate the motor shaft a few revolutions once every 30 days to prevent false brinelling in the bearings and cover the output shaft with something to prevent shaft corrosion. You can also use MCA to checking winding health in storage every 3 months. If no good dry place to store motors heaters can be used in storage to keep windings dry as well but a bit expensive in the long run.
If you are storing them hear a high RF energy environment such as next to a strong transmitting station you should use light gage solder to wire the windings together and to the ground lug.