In reply to Ggilbs:
Yes well but!
As Dan says at the start they aren't checked, YOU have to check them. This is not asking on a forum because it means nothing.
Which is why I asked earlier what you defined as old and not properly maintained since this can only be relative to someone elses opinion, like a perfect stranger on the internet.
I made the bolts in the videos and advised Dan on some aspects as the standard we manufacture to does in fact require us to tell the user how to assess the condition and remaining lifespan BUT nothing is defined in the standard so we don't (same with all climbing gear in fact. The karabiner test is a good assesment for glue-in bolts equalling very, very roughly 1/3rd of the actual standard requirements, for bolt-in not so good but unless you know exactly what bolt you are working with and carry a torque wrench it's just a guess.
Corrosion is a whole different bag of worms, basically you can't see whether the bolt would fail or not, the only real test is to put a tester on it and break it. One persons light weathering is someone else's severely corroded.
Old is relative, plenty of 50+yr old bolts out there.