As long as the ink is still in the original packaging, there is no expiration date.
This reply is coming six years later as I have just registered for this community. I have a Canon E40 cartridge that was given to me from someone no longer using that type of cartridge. She would like me to sell it for her, but I would like to be sure that the cartridge is still good. I have had the cartridge for over a year, and the box only has a lot number to help identify when it was actually made. Any way to be sure I can sell it without worrying about being unfair to the potential buyer?