It is not only light but gases which is generally the greater culprit when fading is an issue. Now since most people don't have a gas analyzer to test for all types of gases in the home, then it is extremely difficult to determine what is causing the problem. It could be something as simple as the type of cleaner used in the kitchen to clean the floors or counters. If it has some kind of agent that causes bleaching then that could be the cause. The other thing is the amount of electric motors in the hose and whether or not there is an electrostatic air cleaner in the heating system.
When I first started refilling, I bought and tested different brands of ink and compared them to OEM on five different media (printer paper, 2 OEM photo papers, and two CDs). in three different locations. It took some time, but it didn't cost a lot because I eventually used most of the ink.
However, I found that one brand faded severely on all media in light, compared to other brands. I made my results known to vendors on this forum. I found two brands that are fairly good. I sometimes use OEM magenta and photo black. I didn't test for gas, of course. I have an original HP print on printer paper that has survived for years on the fridge. I'll have to try some others now.
I don’t think much of Mark McCormick take on 3rd party inks, he’s obviously in a good position to Po Po all aftermarket ink as not worth while, because he can afford to use OEM ink, but then with his next statement says that 3rd party paper can be better than OEM paper, that’s chalk and cheese talk if I ever heard it..
I don't have a reason to question the validity of the Aardenburg or Wilhelm-Research tests as such, the transfer of their data onto a particular real life situation is difficult - how much would the kitchen environment/fridge door scenario have an impact onto their tests and results , or how could I derive the ink performance under these conditions from their synthetic test setup and results ? Their results are useful for a direct comparison , but do not cover another aspect of 3rd party inks - why are consumers using them - for cost reasons - but users are mostly not told by the suppliers that products with a much lower price vs. OEM products may come with shortcomings in their performance - e.g. fading. I have done some testing for my part, I can make a decision to buy and use this or that ink - with both pricing and performance in mind, I'm using the cheap China sauce for prints where fading is not relevant, prints on thermal paper are fading as well, and I'm using the frequently discussed Fuji DL inks when I expect the best fading performance available, or this or that ink , pigment whatever as it fits. But when I get an ink which does not fair well with its price/performance ratio I just don't buy it again, I'm not stuck to a particular supplier or brand or country country.