And again, just like tires, you get what you pay for. At a hare scrambles a few years ago, I was in a pinch for rear pads. Some brake pads have a metal shim between them and the caliper piston. This can be important. You may have a relatively minor symptom like brake squeal or you could have something more important like brake fluid boiling.
Rotors are pretty much maintenance free.
They wear and you replace them or they bend and, if they can t be straightened, you replace them. Bike rotors are not machineable. There are larger rotor kits available. These include a caliper carrier that moves the caliper out to the right place to contact the swept area of the rotor. This can give an increase in braking power for those who can actually use it.