It did not take them long to establish the rule of the fight. For a fight of this level even killing was not enough to end the battle as both of them were able to resurrect many many times. Actually just getting their bodies destroyed was a minor thing and they were able to come back from that almost infinitely and getting the soul damaged was dangerous but not something unrecoverable.
The most important thing for a battle of this calibre was the mastery of laws and concepts. Concept magic was such a thing and even for the warriors they needed to manipulate or break concepts with their weapons or physical prowess. So the battle became a lot more complex.
Actually any being who was above level 5000 would not even be able to fight at all if they were not able to accelerate their thoughts. There were a lot of things to consider in a fight of this level and without faster processing speed, anyone would be overwhelmed.