The overnight session can be as active as the day regarding price-action moves. The times you look for moves is basically 8 PM, 9 PM, 10 PM, and 1-2 AM, all times Eastern US. And then the dreaded 8 AM to Wall Street market open. Sometimes that really kicks ass, or kicks your ass. Like today! hehe
I find that the times you mentioned are easier to trade than the market openings. But a couple of hours after opening, things are getting smoother and easier to trade. The last 30 minutes are also quite profitable to trade most of the days. I also trade the UK/FTSE and DAX/German 30 opening and closing. These are usually less volatile than the US indices. I live in Switzerland - 6 hrs ahead of EST.