I'm aware of the problem with Epson printers clogging up, for that very reason. My daughter's printer clogged all the time and I had to clean it.

I believe the Canon printer is similar to the Epsons in that the print heads are part of the printer. However, their more aggressive cleaning scheme (which I suppose is responsible for my extra ink consumption) keeps it from clogging much.

The aforementioned trick about empty color cartridges is an interesting idea. I wonder if that would work without causing clogs.