Hello spooky8,
I am convinced of the quality of the ink.
I have had an Epson EcoTank printer (ET-2700) since August 2018 and print a lot with it. The first ink lasted me almost three years. I bought a refill set in June 2019 because I had no idea how long such a filling would last. The refill set says "Best before 06 2025". I have not yet noticed any loss of quality due to old ink. However, I usually use high-quality photo paper. Filling the EcoTank is also a clean affair. The valves only open when the respective tank is placed on top. Also, the ink flow stops automatically when the tank is completely filled. I am really very satisfied with the printer and the ink.

Hello spooky8,
I have not had any bad experiences with opened bottles.
I have had half-full bottles stored for over a year and have been able to use them again without any quality defects.
The prerequisite is, of course, that they must be very well screwed (sealed).