My family only likes bananas on the green side, and I never buy more than 5. I also separate the bunch once I get home and lay the bananas spaced apart on the counter.
If bananas go downhill that fast, they are already fully ripe when you buy them, or they are stored near other gas emitting fruits and vegetables.
If you buy bananas at the stage of ripeness you like, but you are not planning to eat them right away, I agree that putting them individually into a ziplock sandwich bag and placing them in the refrigerator, will stop the ripening process and keep them at that stage for a couple of days.
My family does not eat banana bread, cake, or muffins, no banana shakes, so I only buy a very small bunch of bananas each month.