In my experience of testing/using our refillable carts in several different Epson desktop printer models over the years, my results have been pretty consistent over the years, so I don't feel the R2880 or R1900 carts have changed over the past few years (before mid-2011, we had vacuum filled desktop carts with a circular exit channel, then changed to the current cartridge design later in 2011, and have been carrying the same style cart since then). The R1900 and R2880 use the same shape/size/style carts, but with different chips attached.
We have MANY printers in our R&D lab. Some, like our R2880s are used primarily (several times every week), and other models, such as the R1900, 1400, 1430, R2000, R3000 and 3800/3880 are all stored with PiezoFlush and used occasionally when needing to test a specific model. We have storage bins filled with ink carts for each printer model. When we fill a new set of carts, we write on the side to indicate the date filled, and the ink filled with. We leave ink carts in the R2880 printer if we are using it regularly. When we need to install a new set of carts, we remove the first set from the printer, plug the air inlet points, and either put a rubber band around and put them in the bin if they'll be used again soon, or in a sealed zip lock bag if they won't be used in a while. We then install the new set of carts (after moving the vent plugs), and do 2-3 cleaning cycles to purge the previous ink, and get ink from the new carts flowing thru the head. After printing a nozzle check to confirm all channels are fully printing, we test as needed to check ink color, density, color accuracy with a profile, and ink flow consistency while doing back to back printing. We document our results each time, notating everything including printer, cartridge and ink performance, as well as environmental conditions. If we don't have normal good results, we start by cleaning the printer and checking the room temp/humidity. We have a humidifier in our R&D lab, and have noticed the best results when the humidity level is over 30 or 35%. As per the Epson user manual, we try to maintain humidity levels between 40-60% and temps around 65-75F, for the best results with printers, inks and papers. We have a wide range of cartridge ages, ranging from over two years old to brand new. When used and stored properly, we usually get well over a year of good use from carts. Yes, I believe the o-ring seal and exit valve spring can wear out over time of removing/installing carts, and this can effect ink flow. If we experience unusual issues with ink flow, we start by cleaning the printer and checking the room conditions, then if results aren't back to normal, check the carts to see how old they are, and if they have any obvious issues. If we determine a cart isn't working correctly for whatever reason, we will often just replace that cart and continue using the others in the set. If the carts are old, or haven't been properly stored (left out on the counter, and dried out), then we will generally replace the whole set (we try to avoid this, but sometimes get so busy that we can't get to everything in time, though it's good testing to determine what the carts can handle and how they work best). It's very rare that we experience cartridge issues, and generally have very good/consistent results, so I'm puzzled why Brian is still experiencing issues, after we have thoroughly gone thru everything including printer cleanliness, cartridge filling and use, and environmental conditions... It's understandable that Tyler is having issues after years of good results, and has emptied/refilled carts many times while experimenting with custom ink blends, and I expect new carts will resolve issues and work well.
I hope this info of our experiences and practices is helpful. Please keep me posted with your results, and let me know if you have questions or there's anything else I can help you with.
Best regards and happy New Year~ Dana