This will last in the fridge a day or two and can be reheated. Anything over that, the banana starts to go off and it doesn't taste the best.
You can boil water, place oats, bananas, and seasonings into the pot, add the water, and let the oats sit while you do other things. They'll do their thing, start to cook, and then when your ready to eat, simply heat the oats up and cook until they reach your desired consistency, add toppings and voila- fresh hot oatmeal that you don't have to stand over the stove and stir for 10 minutes π
If using frozen berries (which I often do) set the berries out in a container to thaw while you prep your oatmeal. Then when it's time to eat, add them to the oatmeal and they will continue to de-frost without cooling off your oatmeal too much (beats stewing the berries and having one more dish to clean up!)
Find it online: https://modernhomecook.com/simple-banana-oatmeal/