I recently noticed oil building up on top of my valve cover, so I got new bushings for the valve cover studs and after I put them on I left the plastic cover off so I could monitor it. I had some leakage coming from the small hose that plugs into the breather. Not much, but it was there. I clamped down both hoses coming out of the breather with hose clamps, now I have no leakage whatsoever. I only use amsoil 10w30 12tbn, and Purolator or OE filters. Regardless of amsoil's extended drain intervals, I change my filter every 5000kms, and the oil every 10000kms. Naturally I add 1 liter with each new filter, and I burn about the same in 10000kms. Should I be concerned at all?