Why do these shortbread bars bake for about 60 minutes?

They bake slowly so the exterior browns gently while the interior sets without becoming dry. The long bake develops the brown-sugar flavor and gives a tender, slightly crumbly shortbread texture.

How should I store or freeze the bars?

Cool completely, then wrap tightly in plastic and store at room temperature for up to 3 days or refrigerate for up to 1 week. For longer storage, freeze wrapped bars for up to 3 months and thaw in the refrigerator before slicing.