For the following:
HP CB384A Black Drum cartridge 35K page yield at 5% coverage
HP CB385A Blue Drum cartridge 35K page yield at 5% coverage
HP CB386A Yellow Drum cartridge 35K page yield at 5% coverage
HP CB387A Red Drum cartridge 35K page yield at 5% coverage
HP Colour LaserJet CM6030 CM6030f CM6040 MFP CM6040f Laser Printer

Your Drum cartridge will shut down at every cycle of 35K printed pages, leaving you unable to print, even though there may be plenty of toner left in the cartridge.
Slash printing costs by simply replacing the chips which shut the cartridges down, to extend Drum cartridge life by up to 30-40%, or use the chip if you are refilling the cartridges, to get them working again.
Each chip lasts for one cycle of 35K printed pages, after which it must be replaced.