Do what I do, buy the new carts and stick them in. When you get back throw the old carts back in until they're done. There's no waste and you don't risk your print head drying out. You're going to need the damn ink anyway. Just buy it.
I would do this but the last time I did it with an ink at 1, when I went to put it back in I got a message that it was at ink end.... I dont trust my machine.