Aeroplan has fixed a date for when miles must be used.
https://www.aeroplan.com/terms_and_c...entLanguage=EN
22. Subject to earlier termination or amendment of the Aeroplan Program, you can accumulate Aeroplan Miles until December 31, 2019, and request reward travel until March 31, 2020. Reward travel must be completed by December 14, 2020.