I have not said much here, but I follow these discussions daily.
I have multiple stations, an old Davis Vantage, a new Vantage View, and a precision sensor system I am building myself as a calibration unit.
I have experimented with and without fan aspiration for months and I am a STRONG advocate of sensor aspiration. Each sensor, assuming all to be fairly well calibrated, has its own response time to show air readings so it is simply a matter exposing the sensor the real air temperature as quickly as possible without exposing the sensors to sunlight or rain.
To the extent of a sensor's isolation from sunlight and rain, it's readings are delayed. The delay depends on how long it takes the outside air to get to the sensor. I have seen as much as 20 minutes difference in a daily high temperature reading from two good sensors, depending on the shielding, aspiration, and and/or wind.
Good isolation from direct sun and rain is important for accurate temperature and humidity measurements but blowing outside air over the sensor, with a fan, is even better.
I am now experimenting with a simple 2 inch 12 VDC, 1.5 watt computer fan mounted on edge inside my old Davis Vantage Pro and it works very well and gives a nearly simultaneous reading compared to a fast calibration thermometer outside the Davis unit (but in the shade).