Wore these straight out of the box for a full day of errands and had zero break-in issues. The Birkibuc upper feels sturdier than plain leather but still softens up nicely, and the footbed molds to your arch fast.
The two straps adjust independently, which honestly saved me because my feet are slightly different widths. The Birkibuc upper feels sturdy without needing a break-in period, and I wore them straight out of the box for a full day of errands with zero rubbing.