@juergen_hubert Not an historian, but just a thought:

Is it possible that, especially in the culture of the original language, "six hundred hours" could be just a typical expression for "a very long time", akin to the Chinese "Ten Thousand Things", meaning "everything"?

@juergen_hubert There's that bit in one of the Jane Austen novels where they give up on a day trip from Bath to Bristol (12 miles each way) because it's too far. Admittedly they won't have woken up very early in the morning (unlike their servants).

For faster coach travel for people in a hurry, see perhaps some of the Napoleonic era sea stories, which include coach trips from London to one of the south coast ports to pick up their ship.

@juergen_hubert
According to this overview

https://de.wikipedia.org/wiki/Reisegeschwindigkeit#Historische_Entwicklung

people can travel with a 17th century coach ca. 20 to 30 km per hour. Which would mean they would travel ca. 12000 or up to 18000 km.