When you enlisted in the military, either of the three service, you enlisted for the duration of the conflict. In the case of some occupations, your length of service in 'combat' or a 'tour' in the case bomber crewmen was for a prescribed number of operational missions. Having survived to the end of a prescribed number of missions would have meant reassignment to a desk job or perhaps to a training squadron.
In the case of the army and in a frontline unit, you were in until the end of hostilities or demobilization. Only through re-assignment, death, injury or some other medical condition would the length of time at the front be shortened. In the case of a sniper, kill totals only meant he was doing a good job.
With the war coming to an end in NW Europe and with the Western Allies turning their attention to the fight with Japan, Canadians serving were given the opporunity to volunteer for service in the Pacific. This happened before the Germans capitulated so those who sought continued adventure and volunteered to fight the Japanese ended up returning home to Canada sooner than those who had stayed in NW Europe.
When you look at enlistment and terms of servie, you also have the leave policy for those who had joined up early and some were actually allowed to return to Canada on leave. Remember, quite a few WWII Veterans spent six years overseas and for those who were lucky enough to survive, some were in combat units directly engaged with the enemy from July 1943 until May 1945.
If you want the hard facts on enlistment and leave policies, you will have to drill through the various military publications that outline the details.