I have come to this discussion a little late but have a couple of comments from experience with an Epson 3800. A few years ago I bought a 3800 that had been sitting idle for 5 years but had not been used much as it was on its original cartridges. My plan was to use it for Piezography printing from Jon Cone.
Nozzle checks produced large areas of blank space, so, rather than wasting a lot of ink I loaded a set of third party cartridges with Jon Cone's Piezo flush. The initial install put quite a bit of the flush fluid through the printer head but I still had multiple gaps indicating a worse blockage. I had read that the filters that sit on the print head and filter out bits that could otherwise damage the head, can get blocked by ink sitting in them and drying out if the printer isn't used regularly. Altihough these filters can be bought quite cheaply on the internet, they are extremely difficult to install and it is quite easy to break a piece on the head mechanism that governs the printer's use of Photo Black or Matte Black ink.
After I had broken this part I looked for a better solution and found that you can buy a kit that includes the filters, the part that I broke, a new set of ink lines and the cassette that holds the ink cartridges. See part 511 on page six of the attached file STYPRO3800.pdf. This file was sent to me by the Australian distributor of Epson parts. It was readily available 5 years ago. I paid about A$150 for the part and delivery. I also bought a copy of the Service Manual that covers the Epson 3800 and 3880 amongst others.
The Service Manual gives very precise step by step instructions on how to install the part I had bought and after installation and a bit more head cleaning, the printer worked like new. I can't be sure of the source but somewhere in the Epson documentation I have come across the recommendation that this be done every two years on a printer that is being used commercially.
I suspect that a lot of Epson printers get dumped because of a diagnosis of a damaged head when in fact they just have dried ink partially or completely blocking one or more filters. Even with what seems like the overkill of replacing so much, the installation process required very little skill on my part and significantly less cost than a printer head replacement. Equally importantly, there are no electronic parts that need re-setting or calibrating involved so there is no need to pay for Epson technical support, which, at least in my town, seems to be charged at brain surgery rates.
On storing Epson printers, I have read on the Inkjet Mall site, that they sell Piezo flush and cartridges for a range of printers and claim that numerous schools load their printers with Piezo flush, especially during the summer holiday when printers are sitting in school rooms that can get very hot and dry out the normal ink. There is an ink cost in doing an initial fill to remove the Piezo flush solution from the printer in the new term, but this is trivial compared to trying to flush out a dried up printer with proper ink or having to junk the printer because it no longer works.