"Old-age provision" in tea gardens

Teebushes can grow quite old. Some even produce tea leaves up to the age of 150 years, even though in the course of time their yield becomes less and less. That is the reason why India's Tea Board encourages replanting efforts. As the growing of tea bushes takes time and a lot of attention planting is done with a longterm orientation, a sustainable yield can only be expected after 5  to 7 years.