Rotors do wear down. Usually at about 90,000 you think about a new set of rotors with your 3rd brake job. Pads shoudl last about 30,000 miles, you'll have to convert to Kilometers. That is what we find here in the US.
There is a minimum for rotor thick ness and a minimum for pad wear. The reason for this is that the caliper can only push the pads out so far before the caliper assembly would come apart, leaking fluid and not working any more. that is why the minimum pad and rotor thickness exists. Your dealer should be able to tell you what the minmum for the rotors are. Pads should always be replaced when wear indicator starts to light.
To explain minimums.
The distance between the two sides of the caliper is fixed. The rotor wears slowly, so do the pads. As the rotors and pads wear the caliper must push its piston, that actuates the pad out of the caliper cylinder further and further. At a certian point the piston in the caliper is so far out that the fluid behind the piston can start to seal out and leak. This is bad, No fluid, no brakes. So the engineers set limits for the entire assembly. Don't push thses limits.
We find in the US that it is not worth turning the rotors. They are cheap and its easier to replace them. Once you add the labor to remove, turn and replace the rotor. Your better off putting on new rotors. Anytime you R+R you rotors, put on new pads and sensors. You do not hav to replace the sensors IF they had not turned on. Its a plastic covered wire that the rotor wears down the plastic and turns on the wear light. If the plastic has not been dammaged why replace the unit with a new one. Even though they are only $2.00 each.
Why did they not put on a different brake set up. Tthey designed the brake system for the expected use of the car. If you are pushing the car more or havre modified the performance of the vehicle, Consider a better brake system. If your a normal driver, why waste your money.
Do you want larger and cross drilled rotors, with larger calipers that will stop the vehicle much better, You can have it. The after market industry will sell them to you. But why spend $2000 for a brake system you don't need!!!!!
Ventalated rotors, The ventelated rotors are designed to dissapate heat. You're really braking hard and using the car in a high performance mode to need ventalated rotors.
Understand you entire wheel assembly is the braking capability of your car. The amount of surface the pad and the rotor. The design and wear of your tire tread. The surface of the road. The wet dry condition of the road, and again tread design. How much contaminants are on the road, oil, debris, etc.
1970 220D, owned 1980-1990
1980 240D, owned 1990-1992
1982 300TD, owned 1992-1993
1986 300SDL, owned 1993-2004
1999 E300, owned 1999-2003
1982 300TD, 213,880mi, owned since Nov 18, 1991- Aug 4, 2010 SOLD
1988 560SL, 100,000mi, owned since 1995
1965 Mustang Fastback Mileage Unknown(My sons)
1983 240D, 176,000mi (My daughers) owned since 2004
2007 Honda Accord EX-L I4 auto, the new daily driver
1985 300D 264,000mi Son's new daily driver.(sold)
2008 Hyundai Tiberon. Daughters new car