As far as I'm aware, extending those values will only have an affect for as far as the game can load cell data. That's typically two cells around you in any direction, or roughly 12,000 units. Beyond that, you're dealing with LOD, which has no active light data to process.
With the default settings, I could see light sources before I can see their lights in some cases, and that's irksome. For example, a single light at the end of a straight, fogless cave tunnel couldn't be seen until I was a few tileset pieces away from it, and I should have been able to see that light from much further away. Or a guard with a torch at the other end of the Market District - I could see the guard, but not the torch, until the guard was much closer. With these settings, I can see the lights when it makes sense to see them.