Hi Jackie
The visa will last for 4 years from the date it is granted. I've just checked mine for you. The initial entry deadline date is 1 year from when you had your medical, that is why it is important not to get your medical done, till you are asked for it.
i arrived late August this year and we are based in Brisbane, Queensland.
if you want any more advice i will do my best for you, as there are not many people that apply for this visa stream
neil