Well a google search shows warnings as 2 years http://www.cbsa-asfc.gc.ca/publications/pub/bsf5071-eng.html but I read somewhere actual seizure records are kept for 6 years. Of course if actual criminal activity is determined as a result of a seizure likely longer than 6 years I would imagine if associated with a criminal conviction
Also see here http://www.cbsa-asfc.gc.ca/agency-agence/reports-rapports/pia-efvp/atip-aiprp/infosource-eng.html where it says kept for 6 years after which they are archived and not accessable , although maybe that statement applies to public access.
Whether the 6 years applies to someone exceeding their free allowances versus major infringements not clear but these days storing data is so cheap anything is possible.
