Okay this may raise a follicle of disbelief .... But Here goes
If my GS has at least a 1/3 oil showing in the sight glass, I don;t top up the oil... (I work on just between a 1/3 and half on mine )
I don't top it up unless it goes down to below a 1/4
Its a theory a mate of mine and I have that the boxers will find a level that they stop burning oil at
so far 2,500miles its been sitting at around a third full and not changed much level wise