Yep, one of the most valuable companies in the world is 40 years old - Apple Inc.! I first started following them back in 1982 when I was in school - we had a Apple II + in our computer lab, and I followed the still growing computer industry back then, and of course Apple was making the news quite a bit.
While almost all of us thought the company would fizzle out in the late 90's - it obviously didn't and the recovery and market lead is nothing short of incredible. But like everything else in tech, Apple will eventually fade - not away, but not being able to constantly wow the public with every new tech introduction will cause many to think that the company has seen better days.
But I think it will still knock out a homerun or two still in the near future, but really - nothing will be able to compare like the first 40 years this company has had!