You will most likely keep PS from Sept to Jan.
Here is mine, and AFF also says, that you can keep QF status for more than a year, up to abit under 2 actually.
I got to QF PS prior to Dec 14, at Christmas Dec 14, I got to QF SG.
My anniversary is end of Jul 15, so I thought end of Jul 15, I would go back down to QF PS, but no, I get to keep SG from Jul 15 to Jul 16, and if I back date that, Dec 14 to Dec 15 is one year, and from Dec 15 to Jul 16, thats 6 months, so I will have QF SG for 18 months, ie, more than the 12.
If you get QF PS at 250, you will need another 450 QF SC up to your next anniversary.
For me, I did a lot of trips to NZ to make it.
Wait till you make QF SG, then you will be pleasantly surprised.