The 8300 will refuse to print if it thinks it doesn't have enough ink to complete the print that's being sent to it. In almost every case I have waited for that refusal before changing a cart. Bottom line, in a few 10,000 square feet of canvas, I have never run out of ink or messed up a print for ink level issues. But unlike Epsons which prompt you to change cartridges in the middle of a print, the 8300 just refuses to start the print if it's low. However, on a few occasions before starting really big prints, I have replaced a low cartridge just for peace of mind. But I doubt if that was ever really necessary. I don't think the 8300 ever does anything like substituting colors, on purpose.
edit...and once in a while it will ask for a cartridge change just after finishing a print. I have usually looked close at the print on those occasions, have never seen a sudden color change that indicate an out-of-ink situation.