In other types of investigations, 21 days is a decent amount of time. However, in child exploitation cases, that's actually very short, especially when you consider that evidence and reports have to go through multiple hands before they land in the jurisdiction.
One of the challenges is figuring out where a report has to go, because the Internet doesn't have boundaries. A Canadian entity may have to report on it, but that doesn't mean the offender or the suspect is in Canada. There is an administrative process that has to be undertaken simply to figure out what jurisdiction it needs to land on. It passes through multiple hands, and each hand has its own backlog.
By the time it finds its way to an investigator's desk, it can be well beyond 21 days. It can be well beyond 30 days. Sometimes it's several months, and if all of the evidence has been purged before it even gets to an investigator, then the investigation never gets started. Therefore, extending that preservation time to 12 months would absolutely help.