If I understand you correctly the matte black cartridge you have was installed in May of this year. If that is the case you are still good to go. Epson says once a cartridge is installed and the seals are broken the ink is good for 6 months. Honestly, I run cartridges older than that and I never experienced any problems. Just give it a light shake and you should be fine. Always make sure and run a nozzle check before you start any print job when the printer has been idle for over a day.
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