Answer: please see the following.
Mimaki Inks have an expiration date on them to avoid poor print quality. Printer displays the message, [Expiration] to let you know that installed ink passes the expiration date.
Replace the expired ink cartridge.
[How your printer operates in expired ink]
Your printer displays the message [Expiration] in the next month after the ink expiration; and even if you do not replace the expired ink, you still can continue to run it 2 months after the expiration, and when it passes three month from the expiration date, your printer ceases to operate.
If you keep using expired inks, it may result in poor print quality such as degraded colors; we highly recommend for you to replace the expired ink any sooner.