Television shows and films have very short lifespans. A movie may take 1-2 years to make and play for only a couple of months. A television series will run for a couple of years if it ever even gets an audience. Only outliers last more than five years. Product lifecycles and companies themselves are becoming more and more like TV and film. Products last a few years at best. Companies change so much and so fast that workers can't rely on staying at the same place for an entire career.
According to the Forbes article "The Rise of the Freelancer Economy," as of January 2016, there are 53 million freelancers in America. By 2020 it is expected that 50% of the US workforce will be self-employed.
Want to know how to plan your career when the economy consists of products and businesses with short lifecycles? Look to your friends in the film business. They've been doing this for years.