I will try to clarify something here. It is not the experience of a player in a battle that makes the games much longer/shorter (Yes, it has some impact, but imo, almost irrelevant). On the same note, winrate also doesn't necessarily correlate to the length of the games. What does correlate is the way teams are built.    Let me give you an example. My games are usually around 10 mins, even against stall teams. If I gave my teams to you your games would be short, and since you aren't ex