The registration period was previously five years.
"This means that all numbers currently registered will automatically be extended to eight years," said ACMA Chairman Chris Chapman.
"Any new registrations will also be valid for the new period, making life easier for Australians wishing to opt out of telemarketing calls and marketing faxes, long term."
The popularity of the register continues to grow, with 8.5 million numbers now registered.
The Do Not Call Register is a free service where users can list Australian numbers (mobiles and landlines) that are used primarily for private or domestic purposes to opt out of receiving most unsolicited telemarketing calls.
Fax numbers can also be listed on the register to opt out of marketing faxes.
Limited exemptions allow some public interest organisations, such as charities, to contact numbers on the register. Numbers on the register may also be contacted where there is consent from the account-holder.
People can register or re-register their numbers at any time by visiting www.donotcall.gov.au or calling 1300 792 958.