Do insurers have to offer the Age-based Discount?

No. Insurers do not have to offer the Age-based Discount to their customers because the Australian government has made it optional for insurers to offer it.

If an insurer offers the Age-based Discount on a policy, they must offer the Discount to all eligible holders of that policy, including existing and new policy holders.

If you change policies or insurers, it is up to the insurer whether they will or will not maintain your existing Age-based Discount.