The Prime Minister of Canada remains in office as long as they are able to control the majority of votes in the Parliament. As of 2007, a law was passed fixing election dates to every 4 years, but...
Like most parliamentary systems, there is no definite limit on how long a person can be Prime Minister, provided that they retain the support of the majority of the members of Parliament.
There is no limit to how long an Australian Prime Minister can be Prime minister. Elections are held roughly every three years, but there is a very large window of many months which the serving Prime...