Whether or not introducing an air temperature offset error has a long term effect on a vehicle's AFR (air fuel ratio) isn't a matter of opinion, it's a matter of fact. The facts in this case, can be confirmed three ways: Bosch's & BMWs written description of its system (and all Closed Loop ECUs, it's not just BMW that has the "magic"), detailed measurements of AFR (here), and the trim factors that have begun being reported by the GS-911 (Multiplicative Trims, Additive Trims and Lambda Control Factors). The bottom line to all three sets of facts is that Closed Loop systems learn and correct a host of errors, including those introduced at the air temperature sensor. If one wanted to keep the air temp sensor error from being learned and corrected, they could disconnect the O2 sensors just as Techlusion and Power Commander do. However, that then keeps the ECU from making a host of helpful corrections, like adjusting for ethanol content in the fuel, and it puts the ECU into "limp" mode, which spreads fueling both richer and leaner than stock, in an alternating pattern, in an attempt to keep the catalytic converter functioning.