In a recent article in Management Today, Lynda Gratton offers three keys to building a sustainable working life – deep mastery, building a posse of associates and being part of the ‘big ideas’ crowd. In principle I have to agree and, in fact, these ideas seem pretty obvious at first glance. It makes perfect sense to keep up to speed with the latest thinking and to position yourself to be part of the conversation. It also makes perfect sense to build and maintain a responsive network of colleagues and advisors – who’s going to argue with that? But it is the idea of ‘deep mastery’ being an essential component for success that made me think twice.