1. Mix 3½ cups of the milk with the pudding mixes. Beat the pudding mixture with a wire whisk for 2 minutes until it is well blended. Let stand for 5 minutes.
2. Fold 1 cup of the whipped topping into the pudding mix.
3. Arrange a layer of wafers on the bottom and sides of a 2-quart serving bowl. Drizzle 2 tablespoons of the remaining milk over the wafers. Add a layer of banana slices and top with one-third of the pudding.
4. Repeat layers, drizzling wafer layer with remaining milk and ending with pudding. Spread the remaining whipped topping over the pudding.
5. Refrigerate for at least 3 hours before serving.