1)Paper mario SS: 37:04
2)Animal crossing: 36:48
3)Mario & luigi DT: 31:43
I got my 3ds in march 2012, but I'm not that type of person who plays the same game for hundreds of hours unless it's a sports game like NHL 14 or an excellent RPG like xenoblade :P. For reference, I have 22 games on my 3DS and they all have from 10-36hours played.
Predictions for LT console sales:
PS4: 120M
XB1: 70M
WiiU: 14M
3DS: 60M
Vita: 13M