For an extra layer of flavor, consider adding 1/2 cup of chopped walnuts or pecans to the batter. The ripeness of the bananas is crucial for the sweetness and moistness of the bread. The browner, the better! Store leftover banana bread in an airtight container at room temperature for up to 3 days, or in the refrigerator for up to a week. A tablespoon of flax seed meal, mixed with three tablespoons of warm water and left to sit for five minutes, makes an excellent egg substitute if you want a richer taste.