Really depends on the Autobahn though, imho. A3 has nice long stretches, A9 going south from Berlin even more, and again south from Nuremberg towards Munich, A73 going north from Bamberg, A45 was nice before all the bridge works ...
All parts of which 200+ for 15min at a time is feasible. Probs not during rush hour traffic (where it actually happens), but feasible.