30 seconds or less, because we play True20. The question is usually 'Do I charge, or do I attack with a ranged weapon?' or 'Do I set him on fire, or do I mentally dominate him?' and the answer usually involves making one or two D20 rolls on the player's part, and one on my part as GM. Generally, fights take 1-5 minutes per round, depending on the number of combatants.