It seems to make a difference on how the bike has been run. According to local expert, German autobahn run bikes require more adjustment, whereas bikes in OZ with lower speed limits require less frequent adjustment. I've only had to adjust mine once and that was at 140,000 k's, two valves adjusted .025 mm. Coming up to my 160,000 k service and will check them but I'm not expecting to have to adjust them. I've got a local motorcycle shop that will swap them or a local BM wrecker. Even though I've experience very little wear I still wont go more than 20,000 k without checking. I also check rear splines at 20,000 k intervals.
Regards Martin.