Turning rotors is a carry over firm when rotors were upwards of $80-$120 or more each, when they were made much heavier than today. It was well worth the $8.00 to turn one rather than $100 to replace it and they were meant to be turned. Now it is much better to replace if you even think there is warpage. JMO

 

Personally, I'd like to make sure my new pads have a smooth clean surface to grab onto. I guess when it comes to brakes I don't mess around.

 

I changed my fronts at around 60K and the rears around 70K. All four rotors were still smooth, and relatively rust free. I live on the east coast so I would suppose climate and road salt & such play a large part in some owners need to replace or turn them. I have been very lucky in all of the vehicles I have owned I never had to deal with warped rotors. Next time I change them I will consider new rotors or turning them, but for now they stop better than the stock pads.

 

I've done it both ways in the past but I don't do my own brakes anymore, It's not that expensive for a shop to do it. In the old days before ABS, if you didn't turn the drums or cut the rotors, the brakes would grab unevenly and sudden stopping could be an adventure, especially in slippery surfaces. Now days, with ABS, the computer compensates for each wheel and stopping is much more even and straight. So you can get away with just sanding the rotors (assuming they are not warped) to remove the deposited brake pad material.

Now days, the brake pad materials are more advanced and the brakes need to be bedded for full braking performance. Bedding the brakes deposits brake pad material on the friction surface of the rotors so the rotors need to be either turned or sanded. I like the fact that the shops I used for brakes do a cross hone after the machining. Another plus for machining is that it removes the glazed metal surface due to overheating.