A visual inspection is performed at every oil change service at our store. Once a year would be a good recommendation.
Brake fluid can be tested for the PH level. The higher the acid level the more corrosive it is to the seals and solenoids in the ABS / VSC systems.
ABS = anti-lock brakes VSC = vehicle skid control - In our desert climate I would recommend replacing fluid every 3 years.
Scraping or grinding is a serious condition and needs to be inspected ASAP.
Disc brakes "squeeze" the rotor to stop a vehicle. Drum brakes "push" a shoe against the drum to stop the vehicle. Disc brakes perform better than drum brakes. Drum brakes are not used on most vehicles built today.
Calipers are the device that "squeeze" the brake pad to the rotor.
Brake pad material is expensive and have different compositions. Premium pad material will perform better (have better braking ability, are less likely to make noise and last longer) Generic pads use more metal fragments and wear out the rotors faster. More metal will cause noise and heat issues.
Brake rotors are like a thick steel disc. Most are vented in the center to dissipate heat. Brakes use friction to stop a vehicle. The "bigger" the thickness of a rotor the more "heat" it can hold. When you see the area on the side of the road for runaway trucks they are there because when you use your brakes for a long period of time going down a mountain side the brakes will stop working when they can no long absorb heat. Machining a rotor will make the surface clean and straight. The rotor has a minimum specification for thickness. You can usually machine a rotor twice before it needs to be replaced. Machining a rotor is cheaper than replacement.
Larry H. Miller Toyota Peoria