If it has good compression and it does, I would say the oil burning is coming from elsewhere, but since I am not there, there's no way to tell. Valve seals usually dry out, get hard, crack up and fall apart. And of course valve guides wear. When does it smoke? The old adage that when you stand on the gas and it smokes it's the rings and when you let off the gas it's the valve seals and guides usually holds true.