You are so right, Mark. Some of us 3800 and 3880 owners (myself included) are so blasé about their reliability that we often neglect the occasional nozzle check until after a bunch of prints have come out with funny colors.
I had a new variant of this happen to me just a few days ago. My 3800 had been idle for a few weeks and I printed a batch of about ten letter-size prints without a nozzle check first. The colors were way off, so I did a belated nozzle check which showed significant problems on five of the eight active colors. I did a simple cleaning, which made some improvement, but not as much as I wanted.
I then pulled each cartridge and gave each a shake before returning it. Slight improvement. So then I did a Power Clean (I think this is the first one I've ever done in about eight years). I then left it overnight to settle.
The nozzle check next morning showed every color to be perfect, except one. The bad one? The PK (gloss black) cartridge showed absolutely nothing! Yet the Status monitor said that that cartridge was at least two thirds full (although I had noticed that it felt awfully light when I took it out to shake it.) So I put in a new PK cartridge and everything was fine.
We often read complaints about Epson claiming that a cartridge is empty when it still has ink in it. But this is the first time I've heard of Epson's Status Monitor claiming that a cartridge had more ink that was really there.
Anyway, my issue is fixed, I'm happy to say. I'm glad that I have the habit of keeping either one or two spare cartridges of each color at all times.