Actually This is not right Style. As a Canadian Citizen one can live outside of Canada with their spouse. There is no such rule or regulation that says you can live 2-3 months max. The only condition that you have to abide is to return to Canada with your spouse once your spouse gets PR visa.
One have to satisfy and provide proofs to an Immigration Officer about his/her returning to Canada once their spouse will get the visa. You can show that through an employment letter from your employer, or property, or any other proofs or by writing a letter outlining the future plan. However, it is better to avoid staying outside Canada because then you need extra proof to satisfy an Immigration Officer.
But this is NOT correct that you can only stay for number of months with your spouse outside Canada during the whole process. A Canadian Citizen can live with their spouse during the whole application process.