See this from the AP rules:
11.3 Non Expiry of Airpoints Dollars for Nominated Earners of Direct Earn Credit Cards
11.3.1 Notwithstanding clause 2, Airpoints Dollars earned by certain Direct Earn Credit Cards holders will not expire for so long as the credit card holders are the Nominated Earner for the applicable account. Airpoints Dollars earned before the Member was the Nominated Earner, and Airpoints Dollars earned outside of earning them on credit card spend including Flight and non Flight accruals, will also not expire on the same basis.
11.3.2 As soon as the Member is no longer the Nominated Earner for a qualifying Direct Earn Credit Card account, and the Member does not otherwise qualify for non-expiry of Airpoints Dollars, all of their unused Airpoints Dollars that would have expired under clause 2.2 at their last Anniversary Date (or would have expired under clause 2.2 at any other previous Anniversary Date) but for clause 11.3.1 will immediately expire and be removed from their Account.
11.3.3 Airpoints Dollars of Members with a qualifying Direct Earn Credit Card account that is a joint account or has an additional cardholder attached to that account and who are not the Nominated Earner for the account, and who do not otherwise qualify for non-expiry of Airpoints Dollars, will expire in accordance with clause 2.2 of these Terms and Conditions.

Basically as long as your wife is the nominated earner (card is issued to her and the account is hers) then the APD will not expire while she has a card. Be careful if a joint account as I understand that only one person can be the nominated earner.
Call the AP call centre to make sure her card is one of the "certain" cards.