There are 4 available endings. You have not been successful enough in the final battle to trigger the Lia ending. This success depends upon decisions you have made since v0.60.
I would say roughly 20 hours. It depends a lot on how much of the repeatable content you choose to experience. As another guide, there are 112,000 words of dialogue. This is equivalent to about a 400 page paperback novel.
To those complaining about the lack of a harem ending:
The game story and character development is such that what you are defining as a harem ending makes no sense. As a challenge, come up with a concept for what you define as a harem ending and then see whether it is consistent with the characters in the game and their projected futures.
Just because the ending isn't exactly what you define as a harem ending, does not invalidate that there are harem elements through 90% of the game.