What exactly needs replacing disc's, or calipers? I have just replaced my calipers at 120k miles and I did the discs at around 100k. Pads have probably been done at least 3 may 4 times in the life of the car.
So I would say this is normal wear and tear. Having said that, I would say the salt used in the UK roads over winter accelerate the wear, so not sure what "normal" in a warm climate would be.