How far can you go once low fuel light comes on?

I've only ever gone ~30 miles after the light came on. Was that far to a gas station.

I'm going to question the "dirt gets picked up" thing. What happens to that "dirt" in my tank when I drive on rough roads at 60 miles an hour? It's not like our cars ride smooth. I'd guess the fuel in the tank is sloshing around like a blender most of the time. How is it that it magically escapes the pump pick-up when we're driving?

I'm not saying it's good for the car to run it down to the minimum, but there's a difference between logic and merely repeating as gospel what someone else has said simply because it "sounds" logical.