At the 400,000 mark, the phone was subjected to a pretty intense water and dust test and died soon after.

so it did not die from the folding,
but from a "water test" that was obviously designed to break it.

This is the best summary I could come up with:

If you’re wondering how many times Samsung’s latest foldable flip phone, the Galaxy Z Flip 5, might survive when subjected to the stresses and strains of the real world, YouTuber Mrkeybrd has an answer for you: 401,146.

Between August 2nd and today, his channel has run a livestream of the phone being continuously folded and unfolded by a series of testers.

The experiment subjected the phones to a large amount of variation in the speed and force with which they were folded and unfolded, which arguably reflects the kinds of stresses actual people, rather than machines, will put the phone under.

But the Flip 5 appeared to be broadly usable until the 400,000 mark, when it was submerged in water and covered in flour and eggs.

Its hinge appeared to grow increasingly unusable after that point, until the YouTuber called an end to the experiment when a pink line was visible running down the right-hand side of the screen.

In a similar test last year, Mrkeybrd folded and unfolded the Galaxy Z Flip 3 418,500 times before calling the experiment to an end.

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