Think about getting an O-X from Sydney when your O-A expires. You'll get 5 stamped in for 5 years and can leave money in Australia. Must be Sydney consulate.
It's an O-A. You get stamped in for 1 year every time you enter during the visa validity, even on the last day. The border bounce in Feb is the right thing to do.
Or do a border bounce to get the second year before the visa expiry date with extended insurance. It doesn't need to be your Australia trip. But with the the extended stamped date you'd need a re-entry permit.