Around 8pm to whenever I wake up (8-11am). My wife likes going to the kitchen after it's dark(meaning the main light is on/off about 5 -10 times throughout the night) so I try to cut down on the shock to the fish
I got rid of all my live plants and cut my lighting to about 3-6 hours a day most days. Cut my power bill down by about 25%. Next step is LEDs.