It depends. If the cause of the failure is a generic product defect, then I would say they should repair gratis out of warranty. This happens all the time with motor vehicles, where the manufacturers sponsor recalls. If it is not a generic defect, it then becomes the company's judgment as to whether flexibility with out-of-warranty issues would be in their interest. They aren't obligated in this instance.
I think this is much easier to do with a company that does their own repairs, like Canon. I had an OLD Infrant ReadyNas NV+ I bought off ebay for my bro (I had one myself). It turned out it had a bad power supply. But Netgear honored Infrant's "recall" with no questions asked. They sent me a replacement for cost of shipping only.
I wonder how many ink cartridges Epson has had to replace because of all the bad ones. There must have been literately thousands of bad cartridges. They redesigned the packaging twice and issued new firmware to help address it. On the PLUS side, Epson customer service has been great to replace any bad (non-expired) cartridge you have at no cost to you (and also paying for return shipping). Obviously Epson is capable of stepping up to fix a bad situation when it arises.
None of us know for CERTAIN that there is a specific defect in either the design of the new heads, or the (IMHO) overly designed capping station. Yes, there are "lemons" it seems. And this is a great concern for any stuck with one.
Just remember, this thread was started with the intent of trying to learn to fix these things ourselves should we find ourselves in just this predicament.
I don't think that Epson ever admitted any kind of fault for the 4000's constant clogging issues (which was most certainly a result of the capping stations design that also let air draw back into the lines). How did they fix it? They didn't... they came out with a replacement model.
We may never get any admission from Epson the 9900 series printers, but we may eventually get a new printer. For myself, I was of the belief that we had the ultra super sweet printer of all time .... and that my 9890 would have any updates/fixes found wanting in the 9900 release years earlier.
Hopefully all the time, effort and money that Eric has spent will come to fruition, and there will be an answer to these "clogged" nozzles.
BTW: After reading my warranty, I find it unpleasant that should Epson come out to replace your head under warranty, that THEY get to keep all the old parts.