I know that you mostly play Quick Battles Dane, and for those 3h-long battle is optimal for them, but for operations I found 1h to be the best. Otherwise you risk either the attacking AI units not reaching your positions at all (30 mins) or:
- either side completely obliterated (2h+),
- player units out of ammo or depleted and almost incapable of fighting during next battles to come (2h+).
True, the majority of my gameplay are QBs(About 80-20% in favor of QB).
When I do play campaigns though, I generally set my battles to 1H and limited battle radius since I generally only have 2-4 hours to devote to the game at any given time and would like to finish a complete turn in that sitting.
As most of the veteran players have noticed the 2-3 hour turns can lead to some major ammo expenditure and the AI takes advantage of this to send small recon units to get you to expend ammo and reveal your defenses while it grabs territory for flanking maneuvers before launching the main assault which usually won't manifest itself until the last 30 mins. of a battle.
If your willing to engross yourself in the full 3H battle which includes a lot of dead time and set your covered arcs to about 50- 100 meters so your troops aren't firing up everything they see, then some very exciting battles involving maneuver that don't seem predictable can be had. You're not going to get that from the 30 min. to 1H battles.
One day when I retire I would like to play all my campaign battles in real time 3 hour settings so as to really immerse myself in the game and see how well I can keep my troops from wasting the much needed ammo.