Bill Gates' decision to have his foundation shut down by 2045 isn't the norm. John MacDougall/AFP via Getty ImagesBill Gates, Jensen Huang and many of today’s tech titans have two things in common with Gilded Age robber barons like John D. Rockefeller and Andrew Carnegie. After playing a role in propelling the U.S. economy to new heights, they established massive foundations. The foundations are usually designed to last for eternity. Gates is a …