No, 5 hours is definitly to much. Normaly it is about 4 to 4,5 hours. Think of the much traffic not at the highway. And in CZ is only allowed driving 90 km/h outside the city.
531 km in four hours means an
average of 132 kph. Are you really sure that's possible, bearing in mind...:
- the time taken to get out of Frankfurt and into Prague
- the time taken to queue at the border (even in light traffic you have to spend some time crawling along at walking pace)
- making allowance for traffic jams at roadworks, and slower-moving traffic around junctions
???
I can't see it somehow.