I was having a hard time sleeping last night and for whatever reason I started thinking about the film's portrayal of Balin and how to reconcile that with the fact that he goes on to lead a company of dwarves to reclaim Moria some years after the BO5A. After his whole "You don't have to do this" speech to Thorin in Bag End I'm seriously wondering what his motivation would be, because it doesn't seem to fit with his characterization thus far. Unless something happens in the next two films that causes a drastic change in the old dwarf's personality I just can't see him spearheading something so dangerous, so obviously doomed to failure. It seems like he'd be satisfied with defeating Smaug and deeply saddened by the deaths of Thorin & his nephews (if they do indeed die in the final film, which I doubt even PJ would have the gall to alter) so why would he want to risk more lives at his age on such a desperate quest?

The only reason I can come up with is that some younger dwarf (or dwarves) gets the idea in his head and Balin goes along with it out of a sense of loyalty and a desire to protect him/them. Of course we'll probably never see any of that, so again I ask how does that fit with his portrayal in the film? It just doesn't make sense to me