ORIGINAL: LiquidSky
There are lots of occasions where divisions advanced even more then 10 miles a day.
The Russians went 300 miles against the Germans from the Vistula to the Oder. In 3 weeks.
Pretty sure Patton did something similar in the Battle of the bulge.
But that is besides the point [8D]
These are not when in combat, they were breakthroughs. Advances into empty space. Just shuffling counters. Against an enemy unit, a 1 hex advance with 1 day (or even 2 day) turns would be so rare that it would be grounds to have a family get together. You would be playing for RL years before you got one!