Sorry, I posted this under the Magura Julie heading so didn't bother with any more information. I'm 104 kg and got through a set of pads on the front of a Jekyll 700 on a 40 km off road and muddy ride between Reading and Stoke Row in the Chilterns.
I've put the question to Magura and they've asked about the bedding in. They think the brakes need to be bedded in properly with 30*20 mph stops on the road before going off road. I put the new pads on last night so I'll go out on the road tomorrow and then try them off road on Sunday.