Agree, if you are leaving the AMP on, you might just as well leave the preamp on. The ONLY reason i could see not to leave it on, is if the preamp is a tubed model. Though preamp tubes do not wear out nearly as fast as power amp tubes. i have a VAC Standard with four 12a? tubes and i just leave it on anyway. The VAC has not holes or openings and only gets a little warm, so the tubes seem to be lightly loaded.
My amp is connected to the Bryston preamp mute switch, so the amp turns off automatically if I turn on the mute. nice.
My amp is connected to the Bryston preamp mute switch, so the amp turns off automatically if I turn on the mute. nice.