What do you think is the meaning of this album?

I was recently listening to the album "Once" by Nightwish, and I was
trying to figure out the meaning of the album and each of the songs.
According to wikipedia, the songwriter said it was "all up to the
listener to figure out what "once" means"
What do you think?
This question is directed towards people who have actually listened to
the album and most it not all of the songs on it :P