Ahhhh. I love the underlying idea that Dean is the real wall, that as long as he's there nothing else giving way can destroy Sam. And I love the brotherliness of it: Dean in caring protective big brother mode, of course, but also Dean teasing, and Dean getting off on being a hero to Sam. There's a sense all through of the two of them being their own little world of order in chaos, so that as long as they are working wining the cosmic mytharc battles is secondary, and in its sexy, wincesty way that's very true to canon.