My first two to go (the only inks I've changed so far, after about 130 feet of 24" wide printing) were chroma optimizer and photo black. The next three (on the yellow warning state on the front panel for a while, but Canon's yellow warning comes with a ton of ink left) are gray, photo gray and yellow. Just this morning, blue, photo magenta and cyan joined the warning parade, but those have another 100 feet of printing left, maybe more... A lot of the initial cartridges goes into the lines and sub-tanks during setup (not that much is wasted into the maintenance tank, but a lot ends up filling things) - replacement cartridges should last at least twice as long, maybe three times.
Dan