There are a number of reasons why these printers are prone to what appears to be clogging. Firstly, the absence of ink that shows in a nozzle check is not necessarily a clog. It could also be an ink droppage. Ink droppages can occur because of the accumulation of air bubbles in the feed lines. There may be other reasons. So far I have been unable to get a clear statement of the reasons why these bubbles can accumulate, but in principle they absolutely should not be there, so this is a symptom of another defect or defects in the printer.
Second, using this machine at an altitude of 8000 feet is a primary indicator of what the problem may be: your environment may be too dry. Epson recommends - when you ask the question - that these printers should be kept in humidity of about 40%. Get an instrument measuring humidity, place it at the printer, and you may be surprised at how dry your environment is.
Third, if the machine is being used at infrequent intervals, the ink on the print-head can dry causing clogs.
Forth, paper dust can accumulate on the print head, and combined with one of the above factors can cause debris on the print head.
Fifth, the cleaning blade in these machines is an imperfect animal. It sweeps the debris aside, but cannot sweep it off, therefore the cleaning process itself can prolong the cleanings required as debris moves about from one cycle to the next.
Sixth, running cleaning cycles one after another can cause removal of ink from the printhead with nothing to replace it, filling that colour with air. Epson has recommended to run a print between cleaning cycles to minimize this occurrance.
Seventh, it is possible that the capping mechanism on the printer is not sealing the print-head properly, which would allow air to dry the ink and create clogs.
Epson has recommended using a qualified technician to do a head cleaning before resorting to power-clean, which uses alot of ink.
This summarizes what I have been able to learn from several senior technical people with whom I have had the opportunity to discuss this problem over the past couple of years. I should also point out that the 4800 model performs significantly better than the 4000 in respect of ink usage for both printing and cleaning.
There is a review from InkjetArt of the new Canon B9180 which suggests that ink clogs may be an embedded consequence of the technology itself. Here is what that review says about this issue:
<<ELECTROSTERIC ENCAPSULATION TECHNOLOGY (EET). Similar to Epson's UltraChrome inks, the HP Virera pigment photo inks have pigment particles that are covered with a resin layer. What makes the HP Virera inks unique is that their resin layer has negative charges.
<<HP claims these negatively charged pigment particles flow better (the repulsion force between particles helps prevents clumping and nozzle clogging) and helps to create better ink penetration into and onto media coatings -- producing higher gloss (less "gloss differential") on glossy media, improve reliability (more scuff-resistance), and darker photo blacks. While we were not able to prove these claims, we didn't find anything to complain about, either.>>
Now, whether this is marketing hype, techno-babble or a real breakthrough - I have absolutely no idea. Based on very limited experience one also hears that the Canon IPF5000, using a different technology for laying down ink, is very well-behaved in this respect. Clearly the "clean printhead" battle is engaged and that can only benefit us consumers.
Bottom line, I would suggest having your machine looked over by a qualified technician before wasting so much ink/money on a power-clean. Try to get to the bottom of the performance problem before implementing expensive solutions. Then try optimizing the performance of the printer by humidifying its environment, running some prints at least every other day, and when you need cleaning cycles, intersperse them with a print between each cycle as Epson has recommended to me. See whether this package of measures helps. If it doesn't, it would then seem reasonable to consider up-grading to a 4800, or trying a Canon or HP.