You have an Australian CPL and don't know the answers to these fundamental questions ? They were most certainly covered in the Air Law exam. Anyway, if you have an Aussie CPL, then just read it. The validity is printed on the licence.
Of course you also need to go back and re-read the Regs to remind yourself what else needs to be in place for you to exercise the privileges of the licence. You can download all of the required docs from the CASA website for free.
Checkboard's answer is at least partially wrong; Just go and do some simple homework for yourself.