Like some people have mentioned, it's unlikely that the world will end in this generation at the very least, given our limited technology. It's not like we have some kind of orbital death laser to kill everyone, and as insane as an "all the nukes" scenario is, the very insanity of it is the one reason why it'll probably never happen. "Mutually Assured Destruction" and all of that Cold War jazz. Outside of some freak celestial or environmental disaster that we can't see happening nor prevent, I'd say we have a good 100 or 200 years ahead of us.
That being said, I'm honestly very apathetic on the idea of the world ending, much as I am on the inevitability of my own life. Everything has a time and everything dies (thanks Hellblazer), whether it be the world, our lives, or a really good Kiwi Farms lolcow. The best thing you can do is not really think about it and enjoy what time you have. At the end of the day, we're all gonna be dust in the earth, so enjoy what you do. In some ways, Chris is better off than a lot of people because, as huge of a spastic that he is, he's at least enjoying his life. Whether the world ends tomorrow or a million tomorrows from now, I'll honestly be cool with it if I can at least say I enjoyed myself at the end of the line.
.... But in all seriousness, we better have a motherfucking zombie apocalypse. We can all gather up at 14 Branchland Court and turn it into the greatest motherfucking zombie stronghold ever.