I put the DJCs in my s411 not long after it was released and have only ever run my car on a dusty outdoor track. When I pull the front end apart to check bearings etc I usually just check the 'feel' of the DJCs out of the car. Every time they were nice and smooth and I ended up just putting them back in the car as.
Not sure if others give them any special attention but I found them to be reliable and maintenance free with only cosmetic wear on the pins. I did however flip the outdrives as they were starting to get a groove in them.
Regards,
Simon