When I was younger and I drove cars from the 70's and 80's, I had to watch my brakes carefully because if I went too long, the pads would eventually wear down and grind into the rotor and damage them. Not any longer. Today, it seems like it is just a mater of time before the rotor warps. Turning it true again may or may not be an option because the rotors are thinner today. I understand making them thinner makes them lighter and cheaper but I question if it is worth it. On my 70's and 80's cars I probably could have turned my rotors twice before they became too thin to turn again. Today, depending on how warped they are, you may not even be able to turn them once.
I took my wife's Sienna in today because the rotors were warped. If they had turned them the remaining rotor would have been too thin to still be within spec so they replaced the rotors and pads. The rotors and pads had only been on the car for about 35,000 miles. Oh well . . .