there not too bad mines on 134k and still going strong, have done some engine work i.e head gasket valve stems, valve re-grind ect.
oil is as clean when comes out to when it went in when i service it or maybe a little darker

but it is a really clean engine and i'm ocd when it comes to servicing i only do about 3-3.5K a year but i service every 6months. i'm a mechanic so it's not as expensive for me as it is for most people.
but back to my main point, never had a problem with it tapps a little now but i haven't done he tappets since re-build. but it were silent before hand tho.