I remember when I first signed up here for Qantas Club, thinking that would be all that would come of it.
Do you get your 20 JQ flights a year figure from 20 one-ways (10 returns) or 20 returns (40 one-ways)? I ask as I wanted to champion the great value of using the Jetstar Max bundle these days. It wasn't too long ago that a Max bundle cost a
lot more than a Plus bundle, but these days, on a route such as the one you are flying it can be as low as $40 more, and for this you get double the Status Credits (SC), about 50% more points as a bronze (more as you gain status), an upfront/exit row seat and a little more flexibility in your ticket (there are a few other things but I feel these are the key selling points for the upgrade).
Looking at your situation, if you were just taking 20 one-way flights a year (ADL-CNS route) and using a Plus bundle on each, you could expect 300 SC, or enough to qualify you for Silver FF status. This in turn will give you a bonus 250 points per flight, or 5000 extra points a year. However, if you were to change to Max bundles on the route (assuming you could always get them for $40 more) you'd spend an extra $800/year but gain 600 SC (with a Loyalty Bonus you'd be within striking distance of qualifying for Gold) and 10,000 extra points a year. As a Gold FF member, your QP would be put on hold until you couldn't re-qualify again, the 600 SC/year would take you over the line in subsequent years and the amount of extra points you'd earn over a Bronze/Plus bundle member would be 22,500 (that's on top of the 16,000).
On one hand, spending an extra $800 a year can seem like so much more than renewing a Qantas Club membership for $442.80 every year, but I would consider the other benefits the Max bundle gives you that makes it seem quite enticing.
Of course, if you're effectively flying double what you posted per my first query, perhaps Platinum is within reach instead and those lovely Business/First class Lounges!
Welcome to the world of a points and status junkie!