There was also a policy that if you were wounded three times, you were permitted early discharge.
The history MEN, ARMS AND GOVERNMENTS covers manpower policy and is one of the four volumes detailing the Canadian Army's history in the Second World War. The author is C.P. Stacey. The book is available for free download online from the Canadian Forces' Directorate of History and Heritage, or can be found in most university libraries.
Here is the link:
C.P. Stacey's book THE CANADIAN ARMY 1939-1945: An Official Summary, which was published in 1948, is a good precis, as is SIX YEARS OF WAR, which was Volume I of the Canadian Army's official 3-volume history written as an expansion of the 1948 summary.
And here is the link to the official histories:
All are available for free download online, and some of the later volumes can be found in HTML form at hyperwar.com