I do ride rather sedately, compared to what I read in this forum.
However I've found that the most economical speed for the 1100GS which is a compromise between outright speed and outright economy, is about 110 Km/h or something like 68 Mph.
At those speeds one also has a chance to evaluate the scenery, after all isn't that one of the reasons for travelling. If I want real speed then I could travel around a race track, that however, is rather boring in comparison.
Also, if one is able to maintain that as an average, then in todays traffic saturated world, you are a better man than I am Gunga Din.
Mick.