Currently on 3,000 miles on mine and TBH they hardly look worn and not squaring off at all at the moment. I'm pleasantly surprised as I used to get around 4-4,500 miles out of a rear on my 1200GS.
I've been very impressed with the Conti's, especially given how skinny the front is on the 21". They are very predictable, stable and have more grip than I'm able to exploit. They seem especially good in the wet, especialy given the power the bike's trying to lay down - or maybe the TC is doing it's job very well?
Columbo-john, AFAIK there aren't any other road based tyres made in the R wheel sizes (with the relevant speed rating) unless peeps know different? TKC70's are coming out soon in a 21" front but as good a tyre as they seem to be they are never gonna come close to the OEM fitment as a pure road tyre.