Elon Musk’s recipe for global domination? 80-hour work weeks. A person needs to work 80 to 100 hours per week to “change the world”, Musk tweeted this week. The CEO of four companies has said he works 120 hours per week – but research suggests this is a terrible idea. Excessive hours has been tied to heart problems, depression and sleep issues. It’s not likely to make you any more productive. And we’re also prone to exaggerating our work hours; more reason to take Musk’s claims with a grain of salt.