Hmmm... interesting.
I suspect if you're in the business of going back and forth (along the same route), you would in fact be trying to maximise the tailwinds and minimise the headwinds for increased efficiency. In this particular example, I would expect the results not to even out (especially if you're doing your job properly).
In the miltary, when conducting TOT or Elapsed Time navs, the idea was to try and even out the effects of the wind by slowing down when there was a tailwind and vice-versa. This would tend align more with your theory and I would imagine that the results would be similar.
I would therefore conclude that the type of flying you're engaged in would have a marked bearing on the actual result. Unfortunately, I haven't kept any records to back this up with.
Cheers,
P68
