Just stating the facts:
Purchased and installed new Dell Series 21 black and color ink cartridges on 5/25/15.
I have only printed 36 copies using the black and 54 using the color cartridges, and they are both dead/empty/not printing, etc.
According to ink cartridge information I should be able to get at least 180 copies from each.
I hope other people have better luck than I have had.
(I have replace the cartridges many time and was beginning to wonder why it seemed like I was going through a lot of ink. So I kept a log and that is what I recorded.)