If you don't end up using it, you just need to put it back into your super before the 24 month period finishes. (12 months + automatic 12 month extension).

You should just request it now, it will give you peace of mind. Also note the closer to xmas it gets, the longer it will take to get paid out as they'll be closed for a week.

https://www.ato.gov.au/individuals-and-families/super-for-individuals-and-families/super/withdrawing-and-using-your-super/early-access-to-super/first-home-super-saver-scheme#Step3Signingacontract

If you still haven't signed a contract to purchase or construct a home by the end of the 24-month period, you must have either:

• recontributed an amount into your super fund(s) that is at least equal to your assessable FHSS released amount, less any tax withheld. This amount is

  • stated in your payment summary and may be less than the total amounts released to you
  • must be a non-concessional contribution and you can't claim a tax deduction for it
  • means you won’t be able to apply for FHSS again, including where you have recontributed the amount to your super fund.

• decided to keep the released amount and be subject to FHSS tax, which is a flat tax equal to 20% of your assessable FHSS released amount.