Depends entirely on how hard you use the brakes. Your mechanic is obviously very gentle! I can guarantee to have mine down to the wear limit in 50k or so, others will do it in less.
If it's making scraping noises from the back, yours are well past the wear limit, better get the drums checked out, too.
My ones are on about 55,000 miles, and still fine. They will last at least another year (10,000 miles). Mine is only an 899cc Sei, but I doubt that will make much difference. I think 80,000 probably would be pushing it.