OK , my 748E has gone in for main service today (38500 miles). I've explicitly asked for the rockers to be checked out. To my certain knowledge the shims have never been changed either (it has been properly serviced at the correct intervals by people who know what they're doing, though).
Whassa betting?
I'm quite optimistic myself; the bike runs fine, and the oil has been carefully examined at each change. If it needs more than one rocker I'll be very disappointed.
Last owner put 26500 miles on my 748. Pulled the heads last winter. Only needed one rocker surprisingly. I'm tempted never to investigate again, it can only get worse.