Domain names can generally be registered for up to 10 years, but there are a few exceptions to these. The big exception is domains ending in .au (.com.au, .net.au, .org.au, etc) and .co domains. These TLD’s can only be renewed for a maximum of 5 years at a time.
Previously .au domains could only be registered for 2 years but recently with Afilias taking over management of the .au registry we can now register .au domain names for 1-5 years.
Please note, any new .au direct domains that include an application ( contested or non-contested) can only be initially registered for 1 year.