I don't know that it is Too much, but obviously you can cut the algae growth down by cutting down hours of light.
I don't have corals so the light isn't as important, but many days I'll leave my lights off all day until I get home from work around 4 or 5 and turn them off around 9 or 10.
There is plenty of natural light in the room that the lights only make the tank look nicer and if no one's home to see it, you might as well save the electricity.
If you have corals I would assume you could still easily cut down from 10 hours a day.