Until a couple of years ago, when I retired, I took care of our seven dozen
Epson inkjets at school. During the 10 weeks of summer vacation I had each
printer put into a plastic trash bag (expelling most of the air) with a
moist sponge, and tied with a rubber band, then placed in a closet, or
covered with a sheet. Over ten years I never lost one due to clogging.
Your situation for storage though sounds as if it would stretch into
several years. Epson says an unopened cartridge has a lifespan of 2 years
and just 6 months when its placed into the printer. Reasoning for the 6
months is oxidation, fluid vehicle evaporation and thickening of the ink,
which can cause a head clog. So, if you intend to keep your printer tucked
away for a year or more I would be removing the ink cartridges entirely and
replacing them with a cleaning cartridge for each color. Once the cleaning
cartridges are in the printer I would do enough printing as to get the
cleaning fluid to entirely replace the ink inside the printhead. At that
point I would use the same procedure that I use for storing the printers for
the summer vacation.On the other hand you simply put your printer away last
time and then took it out after 4 years and it worked. Sounds pretty
amazing. Maybe it would work again if you were lucky.
P.S. If you wanted to make your own cleaning cartridges fill them with 90%
isopropyl alcohol / 10% ammonia combination.