I agree with Mutt. If constructed correctly, your tankering calculations will also take account of wear and tear etc..
An airline I worked with 5 years ago also applied an environmental premium to the tankering calculation. i.e. although it was commercially desirable to tanker on a city pair, they would add another 5% to the costings before they would tanker.
Another point. Many tankering destinations are isolated (high cost of getting fuel there). If airlines were not tankering into these places, locals would have to import and store larger volumes of fuel. Which in itself may increase the odds of a spill/accident etc..