It's 07:45 departure. Plenty of people in Australia catch domestic flights earlier than that (and luggage cutoff is at T-40, so let's say it's equivalent to a 07:30 domestic departure).
Although for those originating in SIN, most people would probably want to be at the airport at around 05:00'ish for some strange reason. I'd be leaving home at 06:20ish to reach the airport about 06:45, so I'd have 30-40 mins in the lounge. So that's not too early.
