I keep mine indoors, do 3k miles a year, and I'm onto my fourth set of pads and discs all round. I've done 60k in total... Front tyres last about 8k miles. Dammit it's an expensive little toy!
I read somewhere years ago that rear discs can rust easily, due to the lack of use they get. I probably over-compensate for this by using the handbrake to clean them more than I need to