Damn, at least that’s one advantage of living in a pancake country. Still on my original rotor on the back, I probably should check it. Must have done 7k km by now, mostly on the road tho. But still sees lots of bad roads and weather.
You can run your finger on the rotor to feel the groove/lips, if you find yourself replacing pads more often than usual; the rotors is usually the culprit causing accelerated wear.
As @alialias said; road condition play a big roles in this.
Sound about right TBH, especially when his tyres are completely worn out.
Stick to road riding it be less than half that.