I run "CPU always" with 75% CPU usage and GPU only after 4 minutes of inactivity. Those settings aren't too intrusive on my i7, even when playing some games.
My computer is turned on for approximately 8 hours a day on weekdays and I leave it on 24/7 between Friday and Sunday afternoons for extra processing, the computer is on for more hours of the day on weekends anyway so it isn't as much extra time as on weekdays.