Are you using a genuine Brother toner cartridge?
The toner cartridge you are using might not be a genuine Brother toner cartridge. Brother machines are designed to work with toner manufactured to particular specification and will work deliver optimum performance when used with genuine Brother toner cartridges. If you are using cartridges that are not genuine Brother cartridges, your printer may not be able to detect accurately the amount of toner remaining inside the toner cartridge.
Brother strongly recommends that you continue to use only genuine Brother brand replacement toner cartridges. We also strongly recommend that you DO NOT refill the toner cartridge provided with your machine. If damage is caused to the drum unit or other parts of your machine as a result of your use of toner or toner cartridges that are not genuine Brother products, any repairs required as a result may not be covered by the warranty. To protect your investment and obtain premium performance, we strongly recommend the use of Brother genuine supplies.
What types of documents do you typically print on your machine? (For example: memos, documents, spreadsheets and reports, graphics etc.)
The actual amount of pages you get out of a toner cartridge is dependent upon what you print and the amount of toner coverage on a page. You typically get maximum yield of a toner by printing at about 5% coverage which is a small memo or letter approximately 1,500 characters. Print jobs with multiple pages, graphics, charts, and/or large amounts of solid black coverage will use much more toner and will shorten the life of the toner. If you print at 10% coverage, you reduce the overall toner yield of a cartridge in half. For example a yield of 2,500 pages for a standard toner cartridge would be reduced to 1,250 pages when printing at 10% coverage (a letter about 3,000 characters).