I was going to jump at Heavenly Guardian til I noticed you actually can't buy it anywhere so who knows how long before it'd ship if I ordered it. The entry in wikipedia says it was released Feb. 08 in North America but it's not out in Japan yet.. and neither of the Wii versions are released. I...
Between 30 to 40 hours, depending on if you do the optional dungeon or not.
I had 31 beaten without the optional, and then an extra 5 or 6 onto that with it.