It did take me a long time to get to the fourth disc and I did a lot of level grinding outside the Temple of Enlightenment which is good for leveling up your characters but enemy encounters are not very frequent. I learned all the skills for Jansen, Cook, Mack, Tolten and Sed. I also defeated three bonus bosses King Kelolon, Ghost of Eastern Ruins, and the Golden Knight (which gives you the best skill in the game Ultimate Hit).