My experience is the same as Donald's, original cap and rotor and they still look perfect.
Mine has had religious hot oil changes at 3,300 mile intervals.
If there is ANY oil leaking past the cam shaft seal, I would remove the cover and replace the seal. You will need; the shaft seal, the bottom u-seal and the translucent blue, acrylic smelling sealer from MB. With this sealer the cover can be slid rearward over the u-seal without moving the u-seal. Don't forget to gob some sealer at the lower rear corners of the cover area, lubricate the shaft seal, and carefully start the seal on the shaft with your fingernail.