For the following:
EPSON C13S050436 MONO toner cartridge 3.5K page yield at 5% coverage
Your toner cartridge will shut down at every cycle of 3.5K 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 toner 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 3.5K printed pages, after which it must be replaced.