Question?

All of this Christmas election talk has got me thinking about something, and I'm going to rely on my group of readers to provide an answer for me. Let us assume that none of the opposition parties use their Opposition Days to put forward a motion of non-confidence, and instead the big day falls on December 8th when the government introduces its supplementals to keep the engine of government moving. If the opposition parties band together to defeat that, that constitutes a vote of non-confidence and thus the government falls. Does that automatically mean that an election campaign has to begin on the 9th? Can not the Prime Minister or the Governor-General exercise their prerogative power and forestall the call of the campaign until after Christmas, such as the 26th, giving a five-week campaign leading to a vote on January 30th? Surely there is some discretionary power there yes?