Just printing off a 40-page legal document and up pops a "Warning - low ink" message. Oh no the black is running out, I must fit a new one right now. Yeah in HP's dreams. Popped the lid to take a look, the carriage moves and the arrow stops at the 'black low' symbol, the cartridge itself has a small gauge on it, green is full; black is empty, there's a sliver of black pushing at the large expanse of green.
Uh-huh oh yeah that is sooo empty.Of course this is guesswork, the HP cartridges are opaque, unlike my Canon ones which are transparent; so to an extent I'm relying on the software to tell me when they're approaching the end of their life.
Except that it's not accurate, I'm nowhere near running out of ink. If I wasn't standing next to the printer at the time I might have been tempted to pick the "Cancel print job" and gone to check the quality of the print. If I were a novice I might have just taken the report as gospel and simply replaced the cartridge, at £15-£20 a pop that'd soon add up.
Of course that's the point, the manufacturers tend to make next-to-nothing on the actual sale of the printers, instead reaping the profits on the sale of specially formulated inks; it's in their own best interests that you change the cartridges as often as possible.
I know someone who never buys cartridges, he buys a new printer instead - costs him about the same, he gets better technology, and it comes with a starter pack of ink. No doubt the manufacturers hate him.