9th - Granted its an extra 1k AED roughly but what about the skywards mileage accrual that you will get, that fare will go down closer to the time - around 42 days before is the optimum time. If you book on EK now it will be more expensive than say 2 months before hand give or take
Lest we not forget that if you're on full fare you will get treated as such, being on "special" fare you'll still be considered STF so they'll treat you as so.
Last time I flew on an ID ticket I was treated like garbage in comparison so I'd pay the extra 1k AED all day long.