The long drawn out fight is a staple of movies everywhere. Whether it's swords, guns or fists. Five minutes of Wham! Pow! Bang!
It's flashy. It's cool. It also never hapens in a real fight.
Guns sooner or later run out of ammo or someone gets hit. If you've got that much led flying around in the air, it's going to hit something. That's just the rules of statistics.
When it comes to swords the fight can actually be faster. The first thing to remember about movie swordsmanship is that they are not using actual rules of combat. They are not actually fighting. They are performing stage combat. I'm not saying stage combat is inferior. It has a different aim then actual combat (literally). The whole point of stage combat is NOT to hurt your opponent. Though I think movies would be more interesting if they used live (i.e. sharp) blades and real blood, we would go through actors rather quickly. The problem arises when people start thinking that stage combat is what actual combat looks like.
After watching the Saber competition in the Olympics last year a friend commented to me that the bouts were really fast and a little anticlimactic (I didn't bother to mention that Olympic/Sport fencing isn't real combat either, but I digress). If you're used to watching movie fights, then yes, a real fight is going to look like a blur and then it's over.
I actually consider this a blessing as a writer. I don't have to come up with some long complicated fight scene. It's very hard to make an interesting fight last for pages and pages. In my opinion a fight shouldn't last more then a page (at the very most!).
Everything in a fight comes down to timing. The closer matched two opponents are, the narrower that timing becomes, but it still depends on timing. If you’re only a split second off, you’re dead. Quickly.
Most fights are finished in 1-3 moves. Attack, parry, attack in return. End of fight. If your opponent can counter your attack after a parry they're very good. My suggestion in a fight like that: run away.
Of course there are a few exceptions to the quick rule (though I emphasis the ‘few’, as in, theses are the only two I’ve heard of). One duel was between two master swordsmen. Both men kept catching and ripping holes in each others clothes, but neither could get close enough to cut the other. After going back and forth like this for a while, both men stopped, realizing that this wasn't going to end well for either of them. They took the money they had been fighting over, split it and went out for drinks.
Another was a master fencer who was challenged by a total idiot to a duel. The master didn't want to kill the man, so as they fought the only attacks he would make were to snip off the buttons of his opponent’s shirt. Finally the judge residing over the duel called a halt, it was too obvious who had won this duel.
But like I said, those are exceptions. Real fights fought by real people are dirty, bloody and quick. When you're writing a duel or any fight, don't get fancy. Get in, get out, go home alive (hopefully).