The Econoline has existed for over half a century, having been introduced in 1961, and it hasn't changed a lot in that time. The VN platform-based Econoline was introduced in 1975, and has been in use since that time. Though the exterior appearance of the van has changed following updates in 1992 and 2007, many of the core components underpinning the vehicle are pretty much the same as they were 40 years ago. Ford has kept things going by upgrading parts (ex: brake and suspension components, new interior bits, etc) here and there, adding some new engine options over time, and altering the vehicle's appearance somewhat.
The vehicles age still shows, however, so Ford has finally decided to make a change. It stopped making the E-Series in 2015, replacing it with the modern Ford Transit that it has long sold in other parts of the world. This was part of a move by Ford to not only modernize its offerings in this segment, but also to consolidate product lines globally as it has done with the Focus, Fiesta, Escape/Kuga, and Mondeo/Fusion before.
So great is the E-Series' presence and legacy in the North American market, however, that Ford has decided to continue manufacturing its stripped chassis and cutaway models alongside commercial variant of the new Transit, voicing an intent to keep building them for commercial buyers until the end of the decade. Thus, it appears that the E-Series may last long enough to see its 60th birthday.