Conversation so far:
When did Niki Lauda first retire?
In late September, during practice for the 1979 Canadian Grand Prix, Niki Lauda cut short a practice session and promptly informed team principal Ecclestone, that he wished to retire immediately.
What series of races or tournaments was Niki Lauda competing in when he announced his desire to retire?
In late September, during practice for the 1979 Canadian Grand Prix, Niki Lauda cut short a practice session and promptly informed team principal Ecclestone, that he wished to retire immediately.
What type of vehicle did Niki Lauda drive during the Canadian Grand Prix?
What was Niki Lauda's racing record like during 1979?

Question: How long did he stay in retirement?
Self-contained rewrite: How long did Niki Lauda stay in retirement?