I added a battery pack connected to a " try me " button to power the interior lights of a repair shop/store....A model not yet installed on the layout. With multiple bulbs or LEDs in and around a structure the ability to fully light for full visual effect and walk away knowing the lights are killed is a small convenience. Diarama builders might also benefit, especially when the build is on public desplay.
Otherwise, I save them for that day which might never come.
Bruce