I imagine in competitive multiplayer there are longer stretches of time where no openings present themselves because the strategies on both sides are somewhat attuned to one another.
It really depends.
One reason we play at such a slow speed in our group is because there are always small things that can change the course of an offensive and where the timing is important. I can't count the number of times something has gone wrong because someone didn't realize they needed to last stand a division for 12 hours until someone reinforced to width, or that someone simply didn't notice the 25th amphibious invasion of the session that results in the seizing of a key port that should never have fallen.
None of this even address what happens when something truly weird happens.
True Weird Story:
In our current game, Britain left the Home Islands poorly defended during the Battle of France. Due to some custom changes in our mod and house rules, Germany and the Axis can't throw 500 PARA divisions at Britain, and there's enough naval supremacy in place to stop Sea Lion. But someone in the Axis gets the bright idea to drop PARA on Birmingham. We're 99% sure it's undefended, the VP flips the state, and there's basically zero RAF cover over Britain. And we know there are ~13 MIC there. We can't take over the entire British Isles, but this little attack could cost Britain substantially at minimal cost to ourselves.
So, we drop on Birmingham and seize the MIC. Now the player on Britain has to micro the retaking of Birmingham while also running the Battle of France (we have no player on France, and Britain has taken control of French forces). And since the MIC is controlled by Germany, he also has to fiddle with his production, too.
If we were running at speed 4 or 5, he might not have noticed the drop on Birmingham for days, buying Germany precious time to keep that MIC out of British hands. In this situation, every day we sit on Birmingham is a day that he doesn't control his own factories.
Related Lesson: Seriously, garrison key VPs in the interior of Britain or keep a big chunk of the RAF at home. You will be punished otherwise.