*SPOILERS INSIDE!*
I'm twenty-five hours into the game, and I just got to the Calm Lands, right after Yuna and Tidus make out for the first time, and you see them going underwater or something. The weird Japanese music plays, and then Yuna continues the quest. It's after you beat Maester Seymour for the second time (his godly form).
How many more hours until I beat the game, if I'm at twenty-five right now? Please note that I don't plan on doing any side-quests.