Mark, two cartridges that our 7900 came with have expired dates. Want to guess which ones? That's right, PK and YW - our two un-cloggable clogs.
I called Epson, asked them about expired ink causing clogs. They told me expiration dates have nothing to do with clogs - only color shifts. I told them the only channels I have clogs are on my expired carts. Again they told me, "No connection."
I don't know, like I said originally all of you know more than me - I am just an enthusiast. But I don't have much faith in that advice.
What I think our problem was, and what I personally think most of everyone else's problems are, are related to wiper blade condition/wear/effectiveness. The impression I got from holding it in my finger tips, and examining the cruddy splooge built up on it's torn and listing shape, was that this wiper was causing more problems than it was clearing. Once I held our head in my finger tips, and took the photos I have uploaded for everyone here to see, my original impressions were reinforced. Our head was a disgusting mess, and the only thing that's ever touched it is our wiper blade.
I am actively developing my understand of this Epson 7900. So far I plan to approach running it successfully like I might consider lines of defense in a preventive war against clognsplooge. First line of defense is pre-nozzle - dates on carts. Dampers come second. After those we go post-nozzle. Capping station seals. First they need to be in good condition, next they need to be clean. Wiper blades need to be perfect. Not great, not good enough - but perfect. Once not perfect they leave crap behind them on our heads and our capping station seals can't seal properly. Air enters the picture, dries the clognsplooge and suddenly we need cleanings on the LK channel. We do a cleaning and suddenly we've got crap on the MK channel. Then rather than printing we're on Luminous Landscape.
I don't know, I'm not there yet, but my idea for the future is to drop cleaning solution on our wiper blade before any cleaning. Also on the capping station regularly. Periodically I plan to snap out the wiper blade to inspect it. If it is not easily accessible when the head is released I will modify the machine so that it is. Too critical not to. With the right side cover removed you simply reach around back of the pump and cap assembly, spin the gear which lowers the wiper blade assembly until it is accessible, then snap it out/in to replace it. But this is too much work. Too hard to access for such a vital/simple/thirty second key maintenance practice. With the right side cover in place (huge plastic right side outer-body panel) you can't reach around back of the pump and cap assembly to spin that gear. If releasing the head via the menu system does not sync with the wiper blade assembly being out from behind it's recessed hiding place, I will cut a permanent hole in the back of the printer body panel so we can very easily access the gear to lower the wiper. If you can open the back of a human you can open the back of an Epson 7900. This thing pisses me off bad enough I'll design an Epson 7900 wiper blade access door and hire a machinist to produce six hundred to hand out at the next large format printer convention.