both black cartridges "ink end" at the exact same time

[gabagoo]

In 4 years I have never had two cartridges expire at the exact same time, and both the same colour. I now put dates on the cartridges to see how fast they are consumed.

 

[genericname]

Whenever I swap out cartridges for any given reason, I mark the ink level on them with a Sharpie. This helps me keep track of them without having to manually go into Local mode and check them constantly. Serves as a good reminder at the end of the day too, when I may need higher levels for an overnight print.