I did this in December, in economy. I found it perfectly fine, so you certainly shouldn’t have anything to worry about! Make sure you’ve lots of entertainment, whatever that might be, to avoid boredom. That’s what got me through, knowing I might not be able to sleep with the seat.
Getting a shower in SIN would have been far too rushed for my liking, but then it took ages to disembark from the back.
It was my first time arriving in Aus in the morning since I normally take the QR evening arrival. It was noticeably tougher - keep busy on the first day and do not nap!!!