These healthy banana nut muffins will keep on the counter in an airtight container for up to 2 days. u003cbr/u003eu003cbr/u003eAfter two days, store the muffins in the refrigerator to stay fresh for up to a week.u003cbr/u003eu003cbr/u003eYou warm up the muffins in the microwave or let them sit on the counter for 20 minutes or so until they come up to room temperature.