This question has been discussed a lot on the forums in the last year. Generally, though, it's important to remember that almost never has the emergence of an incremental technology meant the obsolescence of something else. This isn't like going from horse and buggy to an auto. Disc brakes solve something that's an issue for some, but not for the vast majority of riders. My current brake pads are 3 years old and I ride more than 1,200 miles a year in rolling terrain. That said, I love fast descents and ride roads where I know I can handle them, which influences brake use.