fwiw, I believe my timezone is the same as PH's (California time), and staying up to launch just past midnight is easy for me.
I think it helps to be around to be around for the first 1-2 hours to see how it's doing, making sure nothing breaks and answer all comments and questions.
If you post on a weekday I saw a big peak just before work (7-9 AM) and then it picks up around 9PM again so try to be around during these times.
That being said, I was #1 on PH and Show HN and went to sleep and everything went fine. I did sleep 2x3 hours so I could reply to everyone that left a comment the 3 hours before that
I suppose it depends how popular it is in all honesty. I've had some launches where next to no one responded and some have been mental busy. I think Europeans are really luck cos we launch in the morning. But really, I wouldn't stress too much. Don't need to respond to every point.
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