[kipchak]

I've done this for a few office Brother laser MFCs. In my experience while you can get a couple hundred more pages out, pages may start being speckled and the cartridge will dust toner into the printer, even if there's still plenty of toner in the cartridge.

From what I can tell this is due to a rubber blade that cleans the toner cartridge's "drum" wearing out, which can sometimes (but not very easily) be replaceable. My guess is that while there's some encouragement of new cartridges going on, the print count is also at a lower number to prevent issues like it from cropping up.

I've also heard that as the cartridge goes through toner, some printers will increase voltage on the drums proportionally, which can be thrown off by resetting the toner level.

From a toner remanufacturing document: "When the printer senses a new toner cartridge, the bias voltage is set to a high voltage. As the cartridge is used, the bias voltage is reduced gradually down. This process is necessary because according to Brother, a new toner cartridge has a tendency to print light. As the cartridge is used, the density increases. To keep the density level even throughout its life, the density bias voltage is reduced accordingly. Each time a new cartridge is installed, the bias voltage is reset to the high voltage point, and the cartridge page count is reset to zero." [1]

Here's a visual of the blades if you're curious. https://youtu.be/UlB832MOUtQ?t=7

[1]http://www.uninetimaging.com/downloads/technical/TecArtWebAd...