Singapore-Beijing Flight Route

I am pretty surprised that the Singapore-Beijing flights for SIA is almost fully booked (a month away) and I am currently on wait-list on another date.. They must be making tons of money from this route.. Anyway, I will be flying twice before the end of the year again. This is to clear off my Kris flyer points and also Qantas dollars. I have about $120 from Qantas (Maybe to Phuket or Bali on Jetstar) and will be using my Kris flyer points to Beijing. I know the flight uses a lot of petrol, so I shall spend my time there wisely to ensure the petrol is well-spent :)