Significance

• The expiration date on an ink cartridge is an estimate, not an ironclad indicator of whether or not it will stop working. Sometimes it's possible to find excellent deals on expired ink cartridges in bulk on sites like eBay and Craigslist that will allow you to keep your printer fueled for much less. If you don't mind throwing out a few cartridges that don't work now and then and enduring the occasional botched page, it's not a bad bet to make. New cartridges can be very expensive, after all.
  
  

Function

• Many cartridges continue to work just fine long after their expiration dates, but many manufacturers have taken to putting timers in their cartridges to make them impossible for customers to use. The rationale given by these companies has been that they would often receive customer service complaints about expired cartridges that would produce ink inconsistently. This would lead people to believe that their printers were functioning improperly, even though it was just the cartridges that were the problem. It also helps to preserve the internal workings of the printer itself.
  
  

Considerations

• If you're using expired cartridges, you may be able to get better results from them by running your printer's cleaning routine several times whenever you start to get streaking or other issues with your printing. Be aware that you may be putting your printer at risk--but not really as much as some of the manufacturers might want you to think. Printer companies are mainly in the business of selling more ink cartridges, where they see far higher profit margins than on the machines themselves .
  
  

Effects

• Learning to use expired ink cartridges properly could save you hundreds of dollars every year, particularly if you print frequently. The best way to store ink cartridges is to enclose them in an air-tight plastic bag with a wet sponge, towel or cloth inside and to then put them in a dark place. This will keep the ink relatively wet and prevent it from deteriorating further. This will help you to keep your cartridges alive if you buy expired ones in bulk.
  
  

Theories/Speculation

• As more printer companies start putting timers on their ink jet cartridges, it's likely that the market for expired ink cartridges will dwindle. Although it is relatively easy to disable the timers, it's enough to induce people to only buy cartridges in small quantities rather than in bulk. This will make it tougher to get cheap expired cartridges online. Until that happens, take advantage of the deals--but be ready to endure mediocre print-outs if you end up buying some duds. Try to only buy cartridges that are a year or two past their expiration date, unless you know that they have been stored properly.