My friends shop have known to get them re-chromed, it works out cheaper and often if done by a reputable company can increase life of the Original, replacement ones. Here's one guy, (appears to be in the U.S) - who's done just that.
Has anyone worked out why the 851 & 888's don't eat their rockers anywhere near as nad as on the later engines? They should suffer from the same oil starvation at start up and (one would assume) be just as sensitive to poorly adjusted valves? Surely if it was just down to bad chroming then Ducati would have got it sorted quickly.
I had mine replated (2 were gone). According to Dave Woods Racing (www.bike26.com) the replating is a longer lasting solution as it is carried out to a higher quality than the factory plating. Still cost 110 quid though
From what i know, Ducati outsourced the production of rockers in 95-96(?) and because of the financial problems they had at that time, they probably chose a cheap producer.
I opened my 916 a few days ago (4000km since the last service) and found only 1 closing rocker on the admission of the vertical cylinder. The rest are fine. I replace it with a 748 one (2000 model) which seem to be of a higher quality... but who knows?
I'm sure that after market ones are a very good options and if i recall Sigma says they last at least 50k miles!!!