Some say that a person should change the work field every 5 to 7 years in order to stay productive and avoid stagnation. How does this apply to academia, for example, changing a research focus?
For example, some universities advise to take a sabbatical every 5 years or so.
Edited as suggested: What are the indicators to show that it is time or an opportunity to change the research area? Perhaps, there is a good answer based on your experience?