Modern inkjets are equipped with the equivalent of air-raid sirens that warn of impending ink outages. The lights on the printer flash frantically. Dialog boxes of doom pop up on you screen. You are running out of ink, they say, the world is coming to an end. Change the cartridge immediately.
Ignore them. In some cases, testing has shown that these warnings appear when cartridges are still as much as 40 percent full [source: Bertolucci]. While newer printers tend to be more accurate than that, the warning system still normally fires when there's still life (or more accurately, ink) left in the cartridge.
If anything, use low-ink reminders as a helpful reminder to buy replacement cartridges. Just don't install them until you absolutely have to. Many ink cartridges have clear or translucent cases, so checking the level is as simple as looking at them.