[Lunatic Pandora]

Would it be wise to stick with the same 4 characters through the rest of the game once you obtain the airship? I just recruited Mog and have watched the events after making it to the end of the cave leading to the Sealed Gate. I wasn't sure if picking 4 characters to level up and obtain magic for the rest of the game was a good decision or not. If it is, which characters should I use?

Thanks!