Today the average American employee stays with a company for less than five years. That number is even lower among younger workers. But many C-E-Os of Fortune 500 companies have spent years at the companies they now run. Walmart’s C-E-O Doug McMillon loaded trucks as a teen. Mary Barra worked the G-M assembly line before she took over the C-suite. Antonio Neri, C-E-O of Hewlett Packard Enterprises, started at the company’s call center back in 19-95.