I beat the first game in 45 hours without doing any side quests and with weak characters (characters with 2000-4000 HP doing 1500-3500 damage to Braska's Final Aeon, Auron doing about 8000 damage after an Armor Break). The second game took me about 60 hours. I got all the Aeons and did some leveling-up and side quests, though I didn't fight any of the Monster Arena creatures or Dark Aeons.