Things to think of too.
As mentioned above, is there somewhere down the "runway" that you can save points for, maybe a flight to CTS, maybe something closer.
Do you need the SC to retain status?
For me, I a lowly NR at the moment, with no hope now (due to finances) of getting to PS/SG, (but have in the past), so I tend to burn my points, either with P+P or buy Y and put in a cash upgrade/points upgrade request, (J as an upgrade award).
If you say you have 8000 or more of QFF points, and are up the QF SC ladder, you could buy that subclass of Y fare, and put in an upgrade request to J.
But for the basic of flying, if you are not interested in attaining/retaining status, using 8000 points plus $40 for taxes for a quick 1 hr flight, is not bad.
Have done that with QFF in the past.
Just used P+P to get back from BNE to ADL, reduced a $190 fare down to about $130 or so, 14000 QFF points, and I still earn 15 QFF SC.