Canada issues multi-entry visas, temporary resident visas that can last for 10 years, so we would have to keep the information for at least as long as the visa or the document for which it is issued. Then we would keep it for some period of time after that to be able to, at least in some instances, help facilitate the approval of the next travel document or the next visa or the next permit applicant.
Part of the benefit we will be getting from biometrics is that it will facilitate the travel of legitimate applicants. If we keep the biometrics for a period of time after that, it gives legitimate applicants the opportunity to apply again and then to establish that they are the same person who applied the last time.