I'd say a big amount of it depends on the campaign and adventure. My current campaign allows the players to choose their adventures, and I provide suggested levels and primary pillar (combat, exploration, or social). Combat adventures usually have 50-75% of the session devoted to combat, but the exploration ones usually only have 25% or so. Social adventures usually have only 1-2 combats for the entire adventure, so 0-10% is about right.