Hi, best source of overall info that you're likely to come across is Henry Wilhelm's encyclopedic book, available for free from his website. As I recall the book was printed prior to the samples you posted, so not directly useful, but the ideas about fading, in general, are valid.
The basic thing is that the dyes in color films are gonna fade over time, some more than others. And it's not unusual to pick up some additional stain. A general rule is that one particular dye in a given film fades faster than the others, so that this dye is the weak link as far as long-term image stability. And there have been huge differences between different films with regard to image stability.
As a general rule, if your negatives have great value, the best thing you could do to help them last longer is to put them into lower temperature storage, with humidity-controlled conditions (read Wilhelm's recs). If you do this you have to be real careful about possible moisture condensation.
There was a time when some of the manufacturers used to publish image-stability data about their films. But at some point I think this turned into a marketing issue. If another company had better stability per testing, they could promote this and even use the competitor's own technical data against them. So such information became mostly secret.
I spent a lot of years with a large chain outfit, and we could get a certain amount of inside test information, but it was all confidential. So the general public, or even pro photographers really have nothing to make judgment on. What we did, in our own facility, was to set up our own abbreviated image-stability testing program. Now, because of the nature of our business, printing high-volume portrait work, our main concern was with the actual prints. (We only held the original film for perhaps 6 months, long enough for people to make additional orders, then after that it was discarded.) Anyway, there was a wide variety in print materials over the years, with a common thing that overall they improved over time.
A little sidenote: I was doing QC work when the current color film process, known as C-41, came out. At one point, at least a handful of year later, a sales guy from someone equipment manufacturer was in my office. He was talking about the early years of C-41, that he had been working in a pro lab at that time, and remarked with that sort of authoritative tone that so many people seem to get, that all of that early film had faded away to nothing. ALL of it, completely faded away. And how, when he had mentioned this to people in such labs they sometimes would go into their files and be surprised that all of THEIR old film was blank. So... I happened to have some very early C-41 film samples in me desk, so said, "Well, let's see." I pulled the file out, opened it up, and... they looked fine. I even took some densitometer readings (in my records were original density readings when that film was new; it was a well-controlled test we had done, including a gray card); the readings were pretty close, but with a definite slight loss in one layer. So the (presumed) B-S "expert" says that, well EVERYONE ELSE'S film had faded, you're the first one that it didn't, etc.
Now, years later, someone from Kodak gave me some image-stability data that they had for several of their films. RememberIng this old sample, I pulled it out. It was one of the films listed. So over the years, every few years or so, I'd pull out the sample and take density readings. My film, held in typical office conditions with controlled temperature and humidity, was tracking right on the money with the Kodak predictions. (They actually showed an "envelope" but my readings were near the center of that.) I continued doing this beyond 30 years, and it still followed the pattern. So these test results showed me that such accelerated testing really was legitimate; it's the so-called Arrhenius testing which is described in Wilhelm's book. Now, for what it's worth, most Arrhenius test results only give an abbreviated result - typically a number of years at room temperature until fade "is objectionable." (The test gives the capabilities to predict dye fading at whatever time and temperature one wants, but this is too complicated for most people. So the normal reporting routine is to say, "well, we think that when the weakest dye fades past a certain proportion of the others that it becomes objectionable, or perhaps just noticeable, and so we report this time duration as the expected "life" of the print, or whatever.
Anyway, it's a complicated subject. For your purposes your best options, assuming valuable negatives, are probably to get high-quality scans now, then find lower temperature storage with controlled humidity. And check for "bad" storage materials (see Wilhelm's book). Best of luck.