The largest brands in the world understand the importance of sustained advertising. They also know why you should never stop marketing. There’s little chance that the people of Earth will forget about giants like Google or Coca-Cola anytime soon, but they reach customers on a day-to-day basis through their online presence and their efforts in other channels.
Even if Coca-Cola did stop marketing, they would probably still make plenty of sales -- they’ve been at it for a while, now -- but they wouldn’t be able to reach new markets, maintain their growth, and continue as an industry leader.