If we're going to include all the chapters where the "final battle" wasn't even being focused on then we might as well just tally up the entire length of the war. This is a war afterall, you're not going to have a single concentration on 1 battle for too long. Especially not the "final battle", at least not until everything else and all the other enemies are settled.
A war where there are a relative handful of actual combatants on one side along with hordes of white trash that's fought on two, maybe three, days in which each side is conveniently bisected by the end of the day and in the end the actual value comes down only to 2.5ish combatants on both sides. May as well label this as the "first great ninja squabble" rather than a war. But in any case, let's not forget that for the longest time, obito was pretty much built up as the final villain with madara as sloppy seconds, so the "final fight" should be counted the moment naruto engaged obito.