I think the freeway link to Mount Martha will be completed over the next year or so... could be an area to consider ? You'd want to be beachside of Nepean Highway mind you.
Coastal areas are a limited resource - most retirees would choose living along the coast and near a nice beach to a shoe box in the concrete jungle and all the hustle and bustle. There are a lot of looming retirees.
I was thinking re: Mount Martha (I wish i had some spare cash right now )- unlike a lot of beachside spots, as the name suggests it's safely above the rising sea levels.
