Joanna Stern built a custom machine that folded an iPhone Duo more than 32,000 times while she slept over four nights, about a year of normal use. The 3D-printed titanium hinge stayed smooth the whole way. Machine measurements had it getting slightly stiffer, though by hand it felt the same as on day one. The plastic inner screen didn't hold up as well: the crease got deeper, easier to see and easier to feel when you swipe across it. Apple hasn't published durability numbers for the Duo, while Samsung claims its newest folding displays survive half a million bends.
Most of that crease is hidden by the matte nanotexture cover on the inner screen. In a video Ice Universe shared on X, people peel the cover off and find a regular glossy screen with a far more obvious crease, and the person doing it says it then looks like the Xiaomi foldable. The cover is glued on tight, and pulling it off yourself could damage the display. Apple has confirmed it's replaceable, for $19 with AppleCare+ or $40 without, so if the crease gets more noticeable over time, a new cover is the fix.