I can vouch for that idea from my own personal experience. Maybe more than a day or so... but I know I let mine set for severalweeks... and I had to do 4 head cleanings to get all nozzles flowing again. It appeared to me that my color management was messed up... posterization in the shadows!!! The head cleanings cleared up the muddiness and my colors are NOW spot on! But I'm pretty sure though that you can go at least ONE week without worrying too much. I've gone over a week without a problem. But I did run a nozzle check then... no clogs.