Had the cap off again today just for a check / clean and you guessed it the carbon brush is worn right down again in around 15,00km - the HT terminals are fine this time . The inside of the rotor also had a buildup of carbon on the brass contact.
Checked the cap height, rotor height, shaft protrusion, spring lenght and brush length against other distributors and it all seems right. Replaced the brush and cleaned rotor so its all good now but

Anyone else see this sort of wear on the carbon brush ? Any thoughts ?
Might be worth checking yours ?