Trying to squeeze every last drop of content out of this game is a strange undertaking as you will go and get every single trophy, collect all major items, get all endings, and go to start a new playthrough. On that new playthrough you end up finding 4 more questlines, and several new dungeons. The same happens again on your next playthrough, and so on. Even when using online resources, you'll still somehow miss content over and over!
Even though I have the platinum trophy and have done 4 full playthroughs with save-swapping to get every ending and do every questline I could find, I wouldn't be surprised if next week I was told there was an entire part of the game I somehow missed.
What a triumph of game design!