The original questions was: "Should an audio system be left on at all times?" I think a more appropriate question would have been "Should an audio system be left on at all times to enhance performance during each listening event", or "Should an audio system be left on at all times to increase longevity"? Frankly, I don't really care about the latter.
For me, it is all about whether my system sounds good when I sit down to listen in the brief windows of time my current life affords. If leaving my source and amp on all the time in order to shorten warm-up period for listening is a valid concept, then I will do that. If not, then I am just wasting electricity. I did not buy this gear to have it sound less than optimal for a period of 30 minutes to several days each time I sit down to listen over many many years. If it breaks, I will replace it with something better.
For me, it is all about whether my system sounds good when I sit down to listen in the brief windows of time my current life affords. If leaving my source and amp on all the time in order to shorten warm-up period for listening is a valid concept, then I will do that. If not, then I am just wasting electricity. I did not buy this gear to have it sound less than optimal for a period of 30 minutes to several days each time I sit down to listen over many many years. If it breaks, I will replace it with something better.