CPF Board requires members to have sufficient funds till age 128? Why?

A letter writer to the Today newspaper, Phan Pang Chia, is asking why the Central Provident Fund (CPF) Board is requiring its members to have sufficient funds in their retirement account to last them till age 128.
His wife was informed by the Board that she will be able to withdraw a monthly payment from the age of 64. The letter further stated, “With the current RA (Retirement Account) interest rate, your RA balance is expected to last about 64 years.”
The letter writer wanted CPF Board to explain why is there a need “for the RA balance to last until the age of 128, when the oldest ever Singaporean was 115 years old.”