All machines have a duty cycle on the spindles. I think that they should do a better job of letting the end users know what this is. I do know thru experience that the air/oil spindles can be run at full RPM for extended periods of time. Unlike the "grease pack" spindles that require a down period.
For moldmaking I would say that the air/oil is a must. Also other manufactures are selling 12K air/oil spindles so one can run say 11.5K primarly without sacraficing much.
Jeff Lange
Lightning Tool & Manufacturing, Inc.