The cake will last for about 5 days when stored in an airtight container.
You can double the recipe.
Baking in two 6 inch pans will give you thick layers that you can slice in two horizontally. You can bake in two 7 or 8 inch round pans for thinner layers.
Sweetness of the cake depends on the type and ripeness of the banana you use.
To make the cake eggfree, you can use 1/4 cup more yoghurt instead of the egg. There is a slight difference in texture.
My measuring cup is 240 ml.