Mom's Banana Bread

I love my mom's banana bread. Here's the recipe:

Ingrediants
1/2 cup butter (113 grams), softened
1 cup sugar (2.4 dl)
2 eggs
2 cups flour (4.8 dl)
1 teaspoon baking soda
3 mashed bananas (I often use four) The riper the banana, the more "banana-y" it will taste
1 teaspoon vanilla
1 cup chopped walnuts (i never use walnuts) I have used chocolate chips on occasion.

Directions
Grease one 9 x 5 x 3 inch loaf pan or two small loaf pans. Preheat oven to 250 F (or 121 C) degrees (I think the secret is cooking the bread for a long time at a low oven setting).

Combine butter, sugar. Cream mixture. Add eggs and bananas. Blend well. Add remaining ingredients. Bake at 250 degrees for 1 1/2 hours until lightly browned.