Shake It Up, Baby
The inks do age and might make for less-than-perfect printing if they are well beyond the date. Whether it would be particulation or evaporation I cannot say - I just would not use one well past the date.
Remember to shake it up, Baby, when you put a fresh cartridge into the machine.
I would also make sure that some little amount of printing was done each week - even just an A4 sheet of a multicoloured test shot would exercise the machinery and ensure that the ink flow though the heads was normal. Each Epson machine has provision on-board to do ink flow analysis and head cleaning and some of the bigger ones can do a very vigorous cleaning indeed. But it uses up ink and the maintenance tank capacity if you are doing it a lot - better to just print each week and keep the problem at bay.
If you are in the habit of stocking up big be sure to look at the dates on the boxes at home and use up the oldest first.
Oh, and paper. Far as I can see paper doesn't expire but if you store it badly you can get some odd results later on. Keep the flat sheets flat and they will stay...flat.