In the Rotax four stroke engines that we race and distribute, plastic-caged bearings are a stock item . However, most of the engine builders in the dirt track "business" seem to think that the plastic cages are for noise reduction rather than separator longevity. They have been known to melt and/or disintegrate under racing conditions .
Another problem is their availability here in the U.S. With high tarrifs tacked on to high prices to begin with, these plastic-caged bearings become difficult to obtain.
Drag racers I have spoken with also believe that the plastic cages are not suitable for aplications such as superchargers.