KAG,
Lubrication is probably one of the more important issues in a preventive maintenance program. The OEM or bearing manufacture will supply you with the correct lubrication and frequency. Many factors come into play, Duty cycle RPM's
etc.
Over lubrication can also be very detremental to machinery. Lubrication technique is also very important. Contaminated lubricants and careless handling of them will bite you in the butt. Mobil has a great web site for correct lubrication practices and they will even come to your facility to educate your mechanics. Hope this helps.
Regards,
Joe