Preheat oven to 325 degrees F. Grease and lightly flour 3 bread pans (9x5) and set aside.
In the bowl of your mixer, cream together the butter, sugar, and eggs until well-mixed.
Add bananas and continue to mix at medium speed until bananas are well-blended. Add the sour cream, vanilla extract, and ground cinnamon and beat just until blended.
Carefully stir in the baking soda and flour just until moistened.
Divide between three baking pans.
Place on the middle rack in preheated oven and bake for 70 minutes at 325 degrees F. Loaves are done when a toothpick inserted in the center comes out clean (may need an additional 5 minutes).
If the tops of the loaves are browning too quickly, place a piece of foil over the bread for the last 20 minutes of baking.
Remove the loaves from the oven. Allow to cool before slicing/storing.
Loaves freeze well; to freeze, wrap in saran wrap, then place in gallon freezer bag and remove the air. Loaves can be frozen for up to one month. Gradually bring to room temperature before enjoying.