Thanks for your reply. I don't change the ink right away either - that was where the notification was handy, cos you knew which was getting low, but there was always plenty to carry on for several docs. Thing is, if one runs out, the printer won't print anything at all till it is replaced. If you don't know which one, you have to do them all. I will try your idea of printing test pages. All I have been able to come up with so far is noting the date that all four were replaced, to try and get a pattern for replacing - but I am sure I will waste good cartridges replacing them too early! Luckily I get them very cheap!