LightGroups.
Switching light on and off, has many benefits and a few
things to keep in mind. When used you basically double the size of your
light data. The game must load information for the lightmaps with the
light ON, and lightmaps with the lights OFF. For some players, this
will mean, it takes longer for the level to load, and require the
engine to keep track of more information.
Best example for Light Groups. SAMPLE_DM , A Lesser Fate
has that switch in the lower sub basement that turns off all the
lights. That is done with this light group set up. Go study it.
If you've made it this far into tutorials, you are already
proved yourself to be diligent and hardworking. None of this stuff is
complicated. It just requires a bit of tenacity.