Main story wise I think roughly 20-30 hours to beat the game, about 8 of that will be level crunching. Really it depends on your gaming style. Could possibly take 40. This doesn't include any side quests or mark hunts. That is just strictly playing from point a to b.

As for side quest there are many hours of side quests, I think I had about 100 clocked when I restarted.

Story wise it is one of the shorter ones of the series, but like all FF's you can make the game as long as you want it to be.