Apple hasn't shared iPhone Duo hinge tests or given a lifetime fold number like Samsung, but Joanna Stern used a custom device to subject her review unit to more than 32,000 folds over four nights.

Over the course of the testing, Stern said she thought it might be feeling looser as the number of folds increased, but her final conclusion was that she couldn't feel much of a change. A calibrated push-pull gauge used to take readings before and after the Duo fold test showed the hinge was actually stiffer than before.

But in everyday use, I really couldn't feel a difference. So, after 32,000 folds, it felt pretty much the same as day one, which is pretty darn impressive.

Stern didn't comment on whether the fold test caused the crease to be more visible, which can happen over time with other foldable devices.…