Reviewer Joanna Stern decided to test what folding and unfolding would do to her review iPhone Duo over time, so she used a custom device to open and close her review unit more than 32,000 times over four nights. She shared the results of her testing, as well as how the machine she used was built, in her YouTube video and in her review writeup.
While Stern said at first she thought it might be feeling looser as the number of folds increased, but her final conclusion was that she really couldn’t feel much of a change. She used a calibrated push-pull gauge used to take readings before and after the testing, and the gauge showed that the hinge was actually stiffer than before.
“But in everyday use, I really couldn’t feel a difference,” she wrote. “So, after 32,000 folds, it felt pretty much the same as day one, which is pretty darn impressive.”
Unfortunately, Stern didn’t reveal how the fold test affected the iPhone Duo’s crease, and if it caused the crease to be more visible, which we’ve seen with other foldable devices.
It should be noted that she performed the tests with a case on, so while the machine opened the Duo completely flat, it didn’t completely close each time.
How do her results with the iPhone Duo compare with Samsung’s Galaxy Z Fold7? Samsung does put their foldable displays through official tests, and revealed in 2025 that the device underwent a passed a 500,000-fold durability test. Samsung Display says that equals to more than 10 years of an average user folding their device about 100 times a day.
Using Samsungs estimates of daily use, Stern’s test equaled almost one year of use.
Apple hasn’t shared any similar official information on display and hinge durability, so we’ll have to settle for the results from Stern’s test at the moment. We can likely see several other unofficial folding stress tests in the next coming weeks.
