The oldest 332 is 22, youngest 12, oldest 380 is 16, youngest 12 and that's with the Covid downtime. All the 787s are under 7.
VH-OJA, the 747 at HARS was 26 when she was finally retired, and plenty of the 747s flew towards the mid-20s.
The narrow body mainline domestic fleet is probably the oldest it has been (oldest 738 22, but youngest 9) but that's just a function of the lump of deliveries post Ansetts collapse, and that's going to change pretty quickly as 321XLRs start arriving from 2025 (think April 2025 for the first)