It’s been a while for me using Twilight, so all I can say is using the different preset rendering settings will give different results with emitters, and be sure to watch the Twilight website lighting tutorial, where they suggest which presets are best for different lighting.
Do you actually have exterior light coming into the space? Time might be cut down by not using an IBL, which may not be adding much to the scene.
Have you tested your various lights? I sometimes test them in a separate file with a super simple scene and see what each light is doing, with no sun, with a given exposure.