It depends on what the purpose is for which you're collecting the information. If, for instance, the information is collected to determine the legality of your status in Canada, I think it's fair to keep it until your legal or illegal status is finally determined. It all depends on what purpose the information is being collected for. It's primarily collected for border management reasons, so there's no one answer as to how long. It depends on what the reason is that it's being collected, and if it's a reasonable purpose, how long does the government need it to achieve that purpose?
On September 18th, 2017. See this statement in context.