The ability to do that will be highly traffic dependent. In practice, driving that fast when possible doesn't shave more than a few minutes time off the overall travel duration from my own experience.
Jep, one minor traffic jam and all the cars you passed at 200 kmh catch up to you. As you do with all those that passed you at 250 kmh. I have that experience multiple times a week. Generally driving at around 130 kmh seems to be a sweet spot, and is by the way the recommended speed on the German Autobahn. It is also much more relaxed. Not that driving fast isn't fun, it is, but going fast in straight lane is among the easiest things to do.
