How long is your recipe supposed to take and what's the oven temp? Mine bakes for 55-65 minutes at 350 degrees. I use a basic quick bread recipe and decrease the milke from 1 1/4 cups to 3/4 cups and add 1 cup mashed bananas (2-3 very ripe bananas). I do find that a hot oven that has been preheated for a long time takes a shorter baking time and a cold oven start takes longer to bake. If the mashed bananas are more than exactly 1 cup (I don't measure the bananas; I just mash 2-3 of them), it will take longer. The type of pan you're using makes a difference. My old, very dark/black bread pans cook differently than my glass pyrex ones. But it's never taken more than 65-70 minutes. Another thought, have you checked the oven temperature to make sure your oven is heating to the correct temperature?
I just finished baking 7 loaves of bread: 2 banana, 2 pumpkin, zucchini, apple, and date. All of them baked about an hour at 350 degrees.