During the last 10 minutes of the baking time if the loaf starts to darken and yet if its not done, reduce the heat to 300 degrees fahrenheit or 150 degrees celsius and let it stay in the oven for 5-10 minutes till done.
I have tried this recipe with whole wheat flour too. Its turns out moist but the texture will be different from that of all purpose flour, as is always the case with baked goods involving whole wheat flours.
You can also try using one cup whole wheat and one cup all purpose flour.
I put the overripe bananas in a freezer safe pouch and leave it in the freezer until i have 3-4 bananas for a recipe.
Slice and store the banana bread in an airtight container in the refrigerator and warm in the microwave or toast as needed.
Wrapped tightly in a plastic foil it freezes well too.