If you are not ready to use them now, you can freeze overripe bananas for use later in baking. This is a guide about freezing overripe bananas.
Do you sometime buy too many bananas? When the outside peel turns dark, don't throw them away. Take off the peel, put in zip lock bags, and freeze until you get ready to bake something.
Those browning bananas on your counter don't need to get thrown away, even if you aren't ready to use them right now. Freezing them is a great way to use them later in banana bread or any recipe that uses mashed banana.
I use to throw over ripe bananas in the freezer to be used in the future for baking. Now I put the peeled bananas in a covered baking dish and cook them for 4 to 5 minutes in the microwave. The pulp will separate from the water.