Ridden disc for years. Signs of a disc worn is when the pads take more than twenty hard pull on the brakes to bed in and outer edges of the pads are shiny. So any advice on enough is enough and change that disc or persist and seat the pad to the disc surface?
I change mine annually on average, use less expensive rotors. I tried rubbing them down with isopropyl and other methods to no avail. When they squeal or grind I change em out!