A:Answer I've left the cartridges set unopened on the shelf for over 1 year. I've had them installed in the printer for over a year...BUT... when the cartridges are in the printer I turn it on every 4-6 weeks, let it cycle, then turn it off. This helps keep the ink in the nozzles from drying and clears them. Yes it uses a bit of ink, but that's cheaper than head repair or replacement.