I have read some posts here regarding the expiration dates of climbing material, especially trad gear. Friends and nuts (as all climbing equipment) have a lifespan of 10 years according to all manufacturers, but I believe the expiration dates of some pieces are longer than our own lives. This is the case with friends, nuts and hexes: there are no parts that should change a lot in time, and even less if you're climbing in mild environments (away from salt water, ice that has a very low pH, etc). Regarding friends, the only part that should be substituted is the sling, and many manufacturers ask you to send old equipment to them so that they can re-sling it for you.
The point here is that climbing is a major (since last week, olympic) sport now, but 60 years ago it was an unorganised niche of potential suicides. There were no companies that would do that for you: people would build hexes and nuts out of old bathroom plumbing, and would sling them with chords and cordelettes. Modern climbing material still teaches how to re-sling old trad gear or build belay cordelettes, which means tying mainly the water knot or the double (ot triple, etc) fisherman's knot, presented below.
Now, keeping in mind people have used both of those knots in climbing for the last century, it's hard for me to believe they aren't safe. I've read that the impact of a hard fall would be enough to "melt" something and then bla bla, but I didn't find any evidence of that on the web. In fact, I think it might be possible to prove that this sentence cannot be true. I have some gear that I have re-slinged with the water knot and it has been catching me every day (this doesn't mean it works, I just might have been lucky 200 times in a row).
Now, does anyone have any evidence of re-slinged material or any of those knots failing?
All those pictures of climbing heroes like Chouinard and Long climbing with dozens of cordelette-slinged hexes on their racks... Were they at risk?