Looking into getting one of these but from what I have found out form the post office applications can be made only 3 months in advance and can only be dated 3 months in advance. I am travelling for a year and need to make use of it in Australia and New Zealand where I will be at the tail end of this year and beginnning of next year. Does anyone have any experiences of driving without an IDP or how to extend it longer etc, and help would be greatly appreciated.
I were investigating a while ago and found this page, in it you have to wait a couple of weeks and the license last up to 3 years.
You don't need an international driving permit in either Australia or New Zealand. (There's only a very few countries in the world where you do; but most only require your drivers license to have its information in english somewhere.)
As for the international drivers "license"/document that Catu linked to: that's a money-making scam that is absolutely useless.