One would expect that these are not normal service items as the wear rate will vary greatly from one driver to another. So I guess they are just changed as necessary. The dealer will check them every time the car goes in for service and in addition to this there are wear sensors on the pads to tell you when they are getting low,so nothing to worry about really . In my experience dealers tend to be a bit pessimistic when telling you about the pads I would always wait until the indicators flash a warning as you could do at least another 10-15,000 miles after the dealer has flagged up that they are low.