Minister of Citizenship, Immigration and Multiculturalism, Jason Kenney, recently announced that Canada will be introducing a ten-year multiple entry visa.  The goal is to achieve a more responsive and flexible processing system.  Currently the maximum length for a multiple entry visa to Canada is five years.
Many countries require a multiple entry visa to enter Canada.  Here is the link which details which countries require a TRV http://www.cic.gc.ca/english/visit/visas.asp
Applications for the ten-year multiple entry visa will be evaluated on a case-by-case basis.  Those individuals determined to be low-risk travelers will be considered as well as parents and grandparents with a family class sponsorship application in process.