Experiment for folks, and your answers may determine whether you need a light on your gun or not.
Pick a time when it is completely dark outside, turn off all the lights in your house. Walk outside, is it brighter outside, than inside your house? When it is completely dark in your house, can you navigate through your house without any lights on?
If it is brighter outside than inside your house, and you can navigate through your house without any lights, an intruder will not be able to see as well inside your house as you can, because they have come from a brighter environment into a darker one. They also don't know their way around your house, but you do.
Another experiment - for those that propose the momentary on/then off use of the 500+ lumen lights inside your house to disguise your position.
On a dark night, with the lights off in your house, sit in some central part of your house, kitchen/living room whatever is a common area. Now have your spouse/child/friend/etc., start in your bedroom and "tactically" work their way through the house using your 500+ lumen light. Decide whether or not you can follow that light as it works its' way towards you.