Rusty brake rotors have been a recurring problem for me. My Firefly (Metro) is on its 3rd set of rotors, with ~37k km / 23k miles on the clock.
It's a combination of two things: (1) very light brake use, plus (2) low distance driven per year. The car regularly sits for a week or 2 between drives, and then when I
do drive it, I may not use the brakes aggressively enough to shine up the braking surface again. Once the corrosion gets past a certain point, the pads won't clean it off.
The solution for this situation is to keep an eye on the rotor surface and remember to do some intentionally harder brake applications once in a while to keep the rotors from becoming a problem.
Also the car is parked outside for half the year, which doesn't help (rotors more exposed to the weather).
The brake pads/shoes, on the other hand, will probably last the life of the car!
(Rusty rotors are possibly even a bigger problem on my
winter beater 2004 Prius because now most of my already typically "light" braking is of the regenerative kind, so there's even
less friction braking compared to the Firefly.)