I never pre-heat my air fryer, I don’t find it necessary.
I prefer the taste of the muffins with chopped almonds rather than walnuts.
Air fryer muffins will keep well at room temperature for two to three days. Allow them to cool completely and store them in an airtight container.
You can also store them in the refrigerator and they will last several days longer.
Or, place them in a freezer-safe container or bag and freeze them for up to two months