When do brake pads need changing?
Most pads have a small metal tab that squeals when they wear thin. That squeal is the warning, and it usually gives you a few weeks. If the squeal turns into a grinding sound, the pad is gone and metal is touching the disc: that wears the discs fast and costs more to fix.
Other signs: the pedal feels soft or sinks, the car pulls to one side when you brake, or the steering wheel shakes when you slow from speed. Each one is worth a check.
How long pads last depends on how and where you drive. Lots of stop-start driving wears them faster than open-road kilometres. We measure them at every service and tell you roughly how much life is left, so it’s never a surprise.