Stumbled across this offer in the Scoot In-Flight Magazine. Appears to have no expiry date, and doesn't ask you to present the advertisement or a boarding pass like some other offers in the magazine. Have not tried it out myself, but might be worth a go if you are visiting anytime soon.
http://www.ink-live.com/emagazines/scoot-magazine/2289/janua…
Might wanna put the state in the title also…