7pm is a good time, set a limit on the day and you get more done, then hit the all important hustle hours of 9-1am hard and your overall productivity will soar in relation to simply staying at work till all ours of the night.
As for sleep. I get about 5-6 hours. I wake up at 7am, at the latest, on weekdays to get the kids to school. On weekends I'll get more sleep (like midnight to 8 am).
It works for me.