The iPhone Duo's hinge was stiffer, not looser, after 32,000 folds, according to a test by reviewer Joanna Stern.
Apple has not shared hinge tests or a lifetime fold rating for the Duo, so Stern built her own. She used a custom machine to fold her review unit more than 32,000 times over four nights, or roughly 8,000 a night. Partway through, she thought the hinge might be loosening. A calibrated push-pull gauge, used before and after, showed the opposite: the hinge measured stiffer than when she started. By hand, she said, she could not feel much difference, and the phone felt about the same as on day one.
The test has limits. The Duo wore a case throughout. The machine opened it flat but did not close it all the way on each cycle. Stern also did not comment on whether the crease became more visible, which can happen to other foldables over time. And the gauge reading does not explain why the hinge changed.
Scale is the useful comparison. Samsung says the display in the Galaxy Z Fold7 passed a 500,000-fold test in 2025. Samsung Display translates that to more than 10 years at about 100 folds a day, or more than six years at over 200 a day. Stern's 32,000 folds are about 6% of that figure. At 100 folds a day, they cover under a year of use.
The two tests are not like for like. Samsung's covers a display and comes with the company's own conversion into years. Stern's covers the hinge on a phone in a case, and it ran for four nights. Neither can stand in for the other.
For now, hers is the only public data point on the Duo, and more unofficial stress tests are likely. The one that would say the most is a test that tracks the crease, the part this one left unmeasured.