Well, I think the greatest evidence is sitting in my reloading closet in the basement.
I have Federal, Winchester, and Remington primers, some of which date back to the early to mid 1990s that I'm cycling through. After the great primer scare/shortage at that time I laid in a large supply, 25,000 small pistol primers, and 5,000 large rifle primers.
Not a single one of the old ones has failed to go off.
If the companies are trying to make their primers go chemically inert after a period of time, they're not doing a very good job of it.