Actually, unless you are a Canadian citizen, nothing guarantees any length of stay. Leaving Canadian citizens, no one else has a right to enter Canada and stay here for as long as they want. Every other immigration status is conditional to something or other. Even PR can be revoked and sent back to their country of citizenship if its conditions are broken OR if Canadian government changes her policy. Noteworthy that even Charter of Rights has a notwithstanding clause, so yeah everything is conditional if you do not have citizenship.
That out of the way, practically, LOTS of people come and enter Canada, legally, and stay here for their authorized period of stay. My parents stayed for one and a half years here (via extension) and now they have a super visa they can stay here for 5 years and an extension of 2 more years, seven years in all, continuously.