You are correct, coG, police certificates are now valid for only 9 months; however, I don't know when this started. My hubby re-did his police certificate earlier this year and it is valid for twelve months.
Further to this, it is up to KG if they want you to re-do your police certificate. It's not like your passport or medical that must be valid when you land in Canada. KG may or may not request another police certificate from you. To be on the safe side and to ensure there is no unwanted or additional time added to the processing of your application you can always choose to get it done again.