Agreed on the pH being <3.5.
I have seen pH <3 reported in some places.
The "as long as you have a clear solution..." clause is total BS, contradicting their own claims made elsewhere. Reason is, my solution turns cloudy after a day (using charcoal filtered, not RO water), but works fine for 3 months. I toss it when it gets "gray," or scummy. I do test the pH regularly and add a few drops of Phosphoric acid when needed.
Again, I've learned early in life to use common sense rather than exp. dates and manufacturers' shelf life BS. They all have ulterior motives, one is selling more product. Another is staying intentionally nebulous about breakdown and spoilage of product.
My concentrate is indeed over 4 years old. I know that, because I bought it well before I moved to my new home, and I've been here almost 5 years. That said, let me rephrase myself: It will last at least 5 years.
I did take the red pill.