How long are your playthroughs? I'm trying to get a sense of how long it'll take me, as I never listen to reviews an how long it takes them FFXIII was apprently 50 hours, and right now I'm 76 hours and I haven't beaten it yet. I like to take my time so I wanna see if this game will be lasting for me.

The game takes about 60 hours with a good chunk of it done.  HOWEVER, the game has 10 difficulties and you start off on the "easiest".  After you beat it, you are thrown into the game again with new crap and a harder mode.  You do this again and again for a total of 10 times.  
 
So you figure being consiervative and being amazingly good and rushing, 40 hours with 10 times is about 400 hours.

10 difficulties...? I can see the achievements for this being really rare.