@auitdreamer It will depend on a number of factors. Number one of course is money. If money is not an issue then next would be how soon do you need to be in Australia?
Answers to these questions will help you decide since you have already received your ITA and decide to lodge, you can also arrange for medical even without COs contact since there is already a link for medical with HAP ID, same is true for NBI/ Police Clearance.
Your answer to the second question is important because the last day of first entry will be dependent on how soon you do the medical or NBI / Police clearance as both have one year validity. But if you will be going to Australia within 2017, then this will not be an issue, do it now as long as you have the money to process everything.
Take my example, I got my invite and lodged the visa on the same day that I got it last December 21 (cut-off of my credit card also, perfect timing I will pay it this February 2017 pa 🙂), but I decided that I should be in Australia by January 2018, so I can't process my medical and NBI this December, earliest possible would be January 3, 2017 because of the declared holidays here in the Philippines. That means if I got cleared on my medical and got the NBI Clearance on January 3, 2017, my last date of first entry would be one year after that, which is January 3, 2018.
For those who got direct grants, they did upload everything including medical examination, NBI clearance, Form 80 and 1221 before the first COs contact (ranging from as early as 5 to latest 30 days from date of lodging). 🙂