Guys, it all depends on who does the servicing. Ducati's service shedules dont require the cams to be taken out. This is the only way to check for rocker wear. Most dealers wont take them out unless you specifically ask them to do so. Nelly for example always checks them. When i went into Chris Clarks a couple of years ago they had never heard of rocker problems!
As regards replacing rockers, you either get a good un or a bad un. Mine is treated well, never raced from cold, 300 miles oil changes etc buit it still needed 3 rockers last time.