There is a very good reason that ink carts have expiration dates. And all you "experts" out there that say it's alright to ignore expiration dates should be aware of ink chemistry and physics before you give such "anecdotal" advise.
First of all, pigments do settle, as some have pointed out. Just shaking the cart can help in this regard, but not totally. There can also be a coagulation of pigment particles. Shaking will not break this up. With enough of these coagulates, your Epson dampers will get clogged and lead to ink starvation problems.
No easy fix for this coagulation problem short of sending the ink back through a grinding process. Much cheaper just to buy new ink.
The modern solvents and co-solvents do a remarkable job of keeping our inks free flowing in our printers. But we should not buy ink in quantities larger than we can't use up within 6 months to a year. And if you go out on a limb and buy expired ink-- you better use it up PDQ and keep your fingers crossed.
The problem most "hobbiest" printers have is they don't use their printers enough. The more you use them, the better off you are.
I'm not affiliated with any vendor or manufacture, and I've warned all of you in the past about the foibles of false economy in using old inks. I can't emphasize enough to use fresh ink, if you want your printer to keep working. Personally, I've had incredible experiences with my 5-year old HP Z3100. Very rarely do I ever Perform nozzle checks, or head cleanings. It just seems to be ready to print when ever I send it files. And I hear similar reports from Canon owners. :-)
I'm curious as to why you think your anecdotal advice is any more valuable than that given by others in this thread? The "experts" here are reporting on experience using specific printers that I would assume you don't even have. Which advice is more useful?
One can't generalize about the physics of ink pigments and how they are affected by age without taking specific printer models into account. With the printer I use, the 3880, your advice couldn't be more incorrect. Eight cartridges, working perfectly for almost 4-years with no head clogging, with no shaking/agitation, in a printer that goes months between printing sessions can't be just luck, particularly when other 3880 users report similar experiences. If you have real data that proves otherwise than I would love to see it. But please don't go around preaching horror stories that are not consistent with the actual experience many other users have had.
Sal