Long Life Consumables...
The Genuine Brother Replacement Black toner cartridge has an up to 10,000 pages yield, and the color toner cartridges have up to 6,600 page yield based on approximately 5% coverage for each color used when printing on A4/Letter sized paper.
When one of the LCD panel squares starts to flash, this indicates that one of the toner cartridges is running low on toner. Order the appropriate replacement toner before you run out.
When you see "TONER EMPTY" message on the LCD panel, the printer stops printing until you replace the toner cartridge which has run out.