Well this is highly displeasing, received this in an email from Virgin Mobile:
As someone who has taken advantage of our Virgin Australia 10% credit back offer in the past, we wanted you to be the first to know that, unfortunately it's coming to an end shortly. We will be taking final bookings for this offer on 6 January 2013. Of course you are most welcome to take advantage of the offer anytime between now and when it wraps up.
Rest assured that we're also talking to all our other Virgin family members about more exclusive customer benefits for you in 2013.
Regards,
The Virgin Mobile Team