Is it burning oil, or leaking oil? Even on a rebuilt engine I've seen some rockers squirt oil every where while others were more subdued.
As long as they are getting oil, then valve train is quiet, and it isn't an oil burner or leaker....... put the valve cover back on and drive it.
Keeping the oil changed at regular intervals with a good detergent oil might help clean passageways a bit, but as long as oil is flowing, run it.
Now if it does use oil, or the valve train is noisy and can't be quietened by adjustment, then it may be time to go deeper into the engine and maybe even rebuild it.
