I've always been told you can choose to have the FTB one either every 12 months at the full amount on Jan 1st, or every 6 months on 1st Jan & 1st july for the halved amounts.
I've actually had it paid in the full amount a few years ago. Seperate to my parenting payment advance.
Maybe that used to be the case but it is no longer. From the Centrelink website:

"From 1 July 2010, if you receive fortnightly payments of Family Tax Benefit Part A, or both Family Tax Benefit Part A and Part B, you may be eligible to receive part of your payment in advance as a lump sum.

When you apply for a Family Tax Benefit advance payment, you will be able to choose to receive either a one-off or a continuous advance payment. A continuous advance payment is paid automatically to you at the start of each 6-month advance payment period, providing all qualification criteria are met. The standard advance payment periods are 1 January to 30 June, and 1 July to 31 December.

The amount of your Family Tax Benefit advance payment may vary depending on when you apply during the advance payment period. Your ongoing Family Tax Benefit payments will be reduced to repay the advance payment you will receive.

You can only receive 1 advance payment in any 6-month period.

To be eligible to apply for a Family Tax Benefit advance payment, you must be receiving Family Tax Benefit Part A. If you only receive Family Tax Benefit Part B, you will not be eligible.

If you have an outstanding Centrelink debt, you will not be eligible for the Family Tax Benefit advance payment until your outstanding debt has been paid. Once you have repaid your outstanding debt, you will be able to make an application for the Family Tax Benefit advance payment."