They say you can never be too rich or too thin, but in this fast-paced world, time is another rare commodity of which we can't have too much. A double oven makes your life easier because it saves you time.
Large, multi-course meals require scheduling and time to rotate all the dishes through the oven. Imagine a Thanksgiving holiday when you don't wake at the crack of dawn to cook the turkey and then have to cook potatoes, veggies and pies -- all while the turkey's drying out. Cooking dishes simultaneously, plus the option to use an oven in warming mode, saves you precious minutes as well as the hassle of reheating before serving.
There is also potential energy savings that come from your double oven. It's true that using both ovens all the time uses more energy, but hopefully, you're not cooking multi-course meals for large groups every day. In the case of a regular meal or just a few people for dinner, use the smaller, top oven that requires less energy to heat. And, in doing so, give yourself an environmentally conscious pat on the back.