Flight Brisbane Airport departs from Brisbane Brisbane Airport at 08:55 and arrives at Melbourne Melbourne Airport at 11:20.
The flighttime is about 2h 25m. The distance travelled ("as the bird flies"): 1343 Km. So the average speed is roughly 556 Km.
The best day to arrive at Brisbane is Wednesday and it would be best to avoid Friday, as prices are on average 30% higher than on Wednesday. (Average prices, based on 1175508 datapoints.)
We have a lot more statistics for flights VA 318 and between Brisbane and Melbourne.