Victoria Miles are valid for three (3) years from date of collection, except when otherwise specified. Some Bonus Miles (such as compensation miles and some promotions) may only be valid for one annual accrual period.
The validity of the miles is in accordance with the date of the activity for which they were awarded.
Before expiry, the validity of miles can be renewed for a fee paid by credit card. Renewed miles are considered Bonus Miles and are valid for another three (3) years.
point 11.
So you need to use them 3 years from the date they're awarded.