Hi izub,
This debate has been on-going for years. It grew out of the vacuum-tube era of recording studios and even early vacuum-tube computers, where there was good reason to leave equipment running. Tube gear takes some time for the circuits to stabilize, whereas solid-state circuitry settles down in a matter of seconds. The surge of power to the tube heater elements was also considered to shorten the life of tubes each time tube gear was switched on. But that just isn't true of solid-state gear used on an occasional basis--even every day-- in domestic applications like home theater and music reproduction.
In reality, unless you are running a studio 24 hours a day, it makes no sense to leave your receiver on all the time. Heat is the enemy of all circuitry over many years, and all components generate heat. This is especially true of A/V receivers, which jam seven amplifiers plus control circuitry onto one chassis.
Look up the idling power consumption in the specs section of of your receiver's owner's manual. It will likely be at least 120 watts if it's a 5.1-channel (or more) surround-sound model. That's like leaving a 120-watt light bulb running all the time. Besides, it offends my sense of energy conservation.
Regards,
