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 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 you clean and align the print head, you should print a nozzle check to determine which cartridges need to be replaced. See Checking the Print Head Nozzles.