I wouldn't worry too much about that. These engines are designed to run at 14.6:1 in closed loop, that really is not going to burn pistons or valves despite the doom and gloom stories of some people. Xieds are more about fixing rider comfort than prolonging the life of the engine.

Its not just about the damage to the sensors, which aren't terribly expensive to replace, its that once you get beyond about 800mV they don't work good and the readings they give are far from accurate.

The difference you will get by going from the recommended max of 14.2:1 to 13.8:1 is a change in AFR of less than 3%, that's not going to help hugely more with engine cooling and at the potential cost of burning out the O2 sensors and them not working very well before that.