When descending long, steep mountain roads in Burundi, why is it dangerous to rely solely on the footbrake while leaving the transmission in neutral or high gear?

1. The brake pads and discs will overheat (fading), leading to complete loss of braking effectiveness; use engine braking in a lower gear instead
2. Continuous braking causes the alternator to overcharge the battery
3. Using the footbrake wears out the exhaust pipe
4. Neutral gear causes the radiator coolant to freeze