Color printer in lab

The color printer in the lab is thirsty for ink.
There's 4 ink cartridges for black, cyan, yellow, red, and they run out in turns.

It all started with the yellow whining that it's low, so we replaced it.
1.5 weeks later, it's red's turn.
Another 1.5 weeks later, it's cyan's turn.
Then another 1.5 weeks later, now it's black......

So is it time to buy yellow again a few days later? Or am I printing too much immunoflorescence microscopy photos?