CPF announced a series of changes in February that, in my view, make it more flexible for individuals to design their own retirement plans according to their own circumstances. The link is here.
You should plan early so that you can design the lifestyle you want (assuming we all live to a ripe old age! ^_^)
Do you know which plan you are going to choose when you turn 55?
There are currently 3 plans to choose at 55 but note that the monthly payout only starts from 65 onwards. This is basically an annuity plan to pay you "till you die".
The reason why the govt allow "property" to be "mortgaged" against the minimum sum is to prevent social issues so that you have a roof over your head while using "$650-$700" per month payout for the monthly expenses for life.