I have a Canon Pixma 9000 Mark II Pro that I've been happily using for a few years now. Lately it seems that cartridges are having to be replaced more often than they used to be and I do less printing on it than I did formerly. There still appears to be quite a bit of usable ink in the individual cartridges (about a half tank) and I'm wondering if the printer is taking its cue from information relayed through the contact points as to how long the ink has been installed and believing it expired.\n\nI don't mind replacing cartridges but I do mind replacing them prematurely particularly at .00 a refill! So what is the printer relying on for its information to signal me a replacement is warranted? Can I safely print with a half tank of ink? Just looking for a bit of advice/guidance.\n\nThanks in advance!