The ETA visa is valid through the date listed in it, which is the last day you have the authority to enter Australia. This expiration date of the Australian ETA will be either 12 months from the issue date, the expiration of your passport, or earlier if a current visa already exists in the immigration system. For example, if your ETA approval is on June 2018, but your passport expiration is in February 2019, your ETA will expire on the same date of your passport; otherwise it will expire in June 2019.