As long as you have had your document authenticated at the Department of Foreign Affairs (DFAIT) in Ottawa and legalized at the Embassy of Mexico, there is no expiry of the stamps of authentication and legalization on your document. However, there are some circumstances where the document itself is only recognized for a specific period of time.
At International Documents Canada (IDC) we have helped many clients with the authentication and legalization of their documents for use in Mexico. We would welcome a chance to discuss your particular needs and make sure it is done right! Call us toll free at 1-888-433-1011 or visit us at idocscanada.ca