Joanna Stern subjects iPhone Duo to 32,000 hinge folds in four-night test

Apple has not released official durability data for the iPhone Duo’s hinge, unlike Samsung’s published fold-count specifications. To fill the gap, technology journalist Joanna Stern built a custom folding machine and ran her review unit through over 32,000 opening and closing cycles across four nights.

During the test, Stern noted that the hinge felt marginally looser as the count rose, but a calibrated push-pull gauge measured the hinge as actually stiffer after the experiment. She reported that in normal daily use she could not detect any perceptible difference compared with the device’s condition on day one.

Stern’s test was conducted with a protective case installed, and the machine opened the Duo flat but did not close it completely on each cycle. She did not address whether the repeated folding made the screen crease more visible, a concern that has arisen with other foldable phones.

For comparison, Samsung’s Galaxy Z Fold7 display underwent a 500,000-fold durability test in 2025, which Samsung Display says equates to more than ten years of typical use at 100 folds per day. Apple has yet to publish comparable figures for the iPhone Duo, leaving Stern’s unofficial test as the only publicly available data point.

Details on the construction of Stern’s folding rig and additional findings are available in her YouTube video and the accompanying review write-up.