Could be from riding the brakes but dont forget that some riders use the throttle more and need to grab a whole lot more brake

I am being serious cause if you pay attention to how often you actually are needing serious braking and how often you change the pads you will find there is a connection.

Most people dont ride too aggressive and therefore get a lot more time from their pads. If you ride lots of water or mud it can have a large effect on the life also.

I have had aftermarket front pads wear out in as little as three rides.

One suggestion on the parking brake is to upgrade to a block off and forget about it alltogether.