"Mike is one of the coolest people I’ve ever know. He’s one of my best friends. I love him to death, he’s an amazing guy, super-talented, so anything he tells me, I pretty much listen to". - Chester Bennington
I just think that Dean would have carried on with this tradition of kissing Sam goodnight for a long time after Mary’s death because it’s something he has done since Sam was born. It would have been something normal when everything else has turned into a nightmare.