How long should an ink cartridge remain in my product if it's not used often?

• When an installed ink cartridge is more than six (6) months old, you may need to replace it if you notice that your printouts don't look as good as they used to. If print quality doesn't improve after cleaning and aligning the print head, you should replace the ink cartridges.
  
  Always leave the ink cartridges installed in the printer until you have obtained a replacement, otherwise the ink remaining in the print head nozzles may dry out.