The PR residency requirements are not being gone from Canada more than 1095 days in any 5 year period. So if you have been PR since Nov 2005 and stayed in Canada total 4 months since then, your PR will be forfeited unless you come back to Canada before you reach 1095 days away (March 2009) and stay for the next 2 years.
There are some exceptions like being married to a Canadian citizen and being with them in another country or working for a Canadian company overseas. You can read about this at
http://www.cic.gc.ca/english/information/applications/guides/5445EA.asp