The $2,000 folding iPhone that goes on sale today starts getting a deeper crease down the middle of its screen within about a week of normal use. Apple planned for it. The top layer of that screen is built to be peeled off and replaced, and Apple will do it for $19. Tim Pan, a YouTuber, put an iPhone Duo on a folding machine and let it open and close 10,000 times at room temperature, then another 1,000 times inside a freezer at -4°F. The hinge still felt smooth at the end, which is honestly…