here is my car, my titanium blacks are drug down pretty far so they only touch here and there. Need to move them down lower:but you get the idea what my mazda 6 can do.
Believe it or not It really dont mess up the roads that much. Just depends on the surface really. Nice smooth white surface throws the brightest sparks. Some guys use trailer hitch balls and makeshit a bracket underneath and bolt on the balls. I dont recommend trailer balls only because it shoots out chunks of metal. but do only cost like 6bucks a piece vise the $60 for titanium drag blocks.
They can last a few months if your easy with them. It comes down to road surface, how hard you lay the car down on the ground, how fast you are going etc.