Any light will travel an infinite distance if it isn't absorbed by anything, and in the far field, all light intensity decreases as the square of the distance. ( What's the far field? In a logically circular definition, it's the area in which the light intensity starts decreasing by the square of the distance.) This is as true for lasers as for any other light source. In looking for a light with the greatest "reach" what you are looking for is a light with the highest candela rating.