Similar to my own experience. For the first 6 months, I got a 10% discount just for having it. But immediately after that, the discount dropped to just 1% - regardless of how little I exceeded 80 mph (never) and how little I hard braked (once or twice a week at first, once or twice a month once I got a feel for where it detected braking) - it didn't matter. I was "grade A" for those categories, but C- for distance. Anything over 7500 miles per year basically removed any chance for a discount.

Now that I live much closer to my job, I could probably qualify, but I also found a little stressful to always be worrying about maybe triggering the "hard braking."