After investigating some of the recent changes in the budget, there is a lot there for early retirees.
Firstly, people can add concessional contributions to super when they're not working.
Secondly, if you have less than $500k in super, and haven't deposited all your allowed concessional contributions in the past 5 years, you can add whatever you haven't at once.
Together, this means early retirees can wait until they reach their preservation age (or until they are sure they'll make it to preservation age with their non-super stash) to deposit up to $125k of concessional contributions. Since concessional contributions reduce your income, it means that CGT for moving a stash from outside super to inside super is significantly reduced, and you can possibly deposit non-concessional contributions at the same time (up to $300k with the bring forward rule) and still have minimal CGT. I haven't done the calculations, but it could be quite significant for early retirees, and a way to transfer up to $425k at once from outside super to within it.