3 Times, in each case, just under 6 hours... 2 of them where pretty much "overnight".
1st time -PER-xMEL-CBR, thanks to daylight savings ending in the eastern states that night coupled with very favorable winds, arrived at MEL at around 3am (don't remember exactly) and left for CBR at around 8am (again don't remember exactly). We both wandered over to the Int terminal and I'd never been so happy to see a McD's open, esp at 4am. About 5am the QP opened and we went up there to try and get some shut eye.
2nd time - RAR-xAKL-xMEL-CBR, We caught the flight out of RAR arriving at AKL at around 1am from memory. We did the transit security thing to find that everything was shut (there would have been 50 or so people stuck airside, I'd bet most of them would have brought a coffee if a coffee shop was open). Our flight to MEL didn't start boarding until 7am (about 30 minutes late). On arriving in MEL around 8:30am, we then had to wait until 1:30pm for our flight to CBR. (Sunday schedule)
3rd time - CBR-xMEL-PER, I was original booked on a nice sensible 1.5 hour connection, however that morning QF called me and said that my CBR-MEL flight was probably going to be cancelled (which it was so it was a good move on my part) and would I mind taking an earlier flight. The annoying thing was the earlier flight got me down to MEL around 6 hours before my flight to PER. I thought it wouldn't be so bad, just go into the QP and kill time there. The thing is that after 2 hours in the QP it got really boring, so decided to go for a walk around. At least the first two times I had someone to talk to (although in the first instance, my friend had that look of murder in his eyes). This time I was by myself, not exactly fun. Prob was that I could have probably left the airport, but everyone I knew in MEL at the time were all working. I did also try and get on the earlier PER flight but with no avail.