He doesn't need to extend his battles, that Aokiji & Akainu and Ace & Jinbei fought for several days doesn't really matter. That they fought for so long simply means two things: they have huge stamina and far more importantly their powers are practically even and then I'm not talking about something like they're the same tier, but that they're evenly match to the smallest of details. So that they fought for a long period of time really should not be used as a parameter for the lengths of other characters fights. In theory two characters who are stronger than either of the above mentioned ones, could have a fight that ended in one second depending on the difference in strength between the two characters and the nature of their abilities. Same thing for characters that would be weaker, they could likewise have a lengthy fight as long as their stamina allows it and the difference in power and ability is exactly even.
Akainu and Aokiji were two admirals, one using magma and the other ice. Jinbei was a Shichibukai and Ace was someone invited to become one, one using water and the other fire. Both strength wise as ability wise these match-ups were almost completely even, there was nothing that could give one person the edge over the other, but this really does not apply to most battles where there's a difference in strength and/or a difference in the abilities used that could give one character the edge over the other. So no there is really no need to have fights that last 10 days on screen.
Also that simply does not work. It's really no coincidence that both of these lengthy fights almost completely happened off-screen. In essence what happened during those fights wasn't important, only the result was. Someone had to become the new Fleet Admiral, but that Akainu and Aokiji fought 10 days for that position was really not important, that was just to make it more interesting for the story. You can't have a battle for 10 days on screen, that would take a hellish long amount of time to draw unless you would start skipping large parts of the fight. However if you do that, it means the fight itself was not important which in return makes it redundant to have a fight lasting so long.