To answer your question (briefly ), I do arround 3000km per year on german Highways.
You can no longer as in the past go as fast as you want for ever because there are at about each 10 to 15km a restriction to 120km/h and police is nearly always there with their laser guns. Anyway, when driving there, people always respect speed limitations but when they are free to go, woooow... A good average of 150km/h on the right lane is very pleasent. If you go on the left lane, rules change, must be VERY carefull when you change lane because a car can suddenly appear in your mirror and pass you within a second... They drive at over 200km/h.
I usually try to go as fast as I can with my 560SEC. I easily reach 250km/h (shame that it is restriced), the car is very safe and you feel that you still have control on it, brakes are useless at these speeds so if a crazy man changes lanes, you'd better find a route on the side or somewhere because otherwise you are simply dead.
I used to have a 500SEL, the car at 220km/h was not really safe and it's top speed was ~230km/h.

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