Work out you benefits very carefully. You mention that you don't spend a great deal on credit cards, so the points balance is not going to grow quickly. Compare with some business people who can spend tens of thousands of dollars a week on their credit card and seek limits uo to $100K.
And keep in mind that the QF Frequent Flyer program has two purposes:
- Retain loyalty to the Qantas brand for people flying a lot
- Make money for Qantas by selling points to partners such as Credit Card providers
And it sounds like you will fall into the second category. Note that there is not necessarily anything in it for you. You will earn points, but then need to be able to redeem those points for something useful. So think now about what you plan to achieve from your points.
As someone who is not a high status QF FF member (at least Gold and preferably Platinum) you will be unlikely to be able to use your points for flight upgrades to business or first class. So you are limited to using them for award flights. Unless you earn a significant number of FF points, you will be limited to domestic flight awards. Note that Qantas make the FF members pay all the surcharges and taxes (including QF's fuel surcharges) when then redeem FF points for award flights. So you have to weigh up the value of using FF points for an Australian domestic flight and paying the fuel surcharges and taxes, verses just buying a cheap fare when they have a sale (seems like almost every week at the moment).