If you do anything for too long it becomes obsessive and you get raggey and difficult, it's nothing to do with Minecraft per se. My kids play and watch Minecraft amongst other things, just return his laptop to him gently starting with an hour or so to begin with and make sure he has breaks and isn't only doing one thing on it. Don't make him feel punished for enjoying something, but make it clear to him that EVERYONE'S personality alters if they do something too much, and ask him to be self moderating and see what he comes up with as far as ideas and then discuss it and work out what is and isn't acceptable to you. It's far easier to have a kid whose on side than one whose confused as to why you've stopped him doing something he enjoys.