Leave it on?

My source component and my amps have a standby feature. The manufacturers both recommend turning them off when not listening. They do sound better after fully warm. I turn everything on 30 minutes before starting to listen and we're good to go.

@mylogic  - You seem to have very little of it; logic that is! I believe you're on the wrong forum, and should be on the Tree-Huggers forum, elsewhere!

How long will you keep your new gear? = Irrelevant to this discussion.
How do you feel about global warming? = Irrelevant to this discussion.
How confident are you leaving other appliances on all day and night? = Irrelevant to this discussion, as we're not talking of washing machines or fridges here!
How would you feel if your house burnt down? = Irrelevant to this discussion.

@maprik Naim and MANY other manufacturers advise to leave their equipment on 24/7/365 for a reason, and that reason is to gain the maximum sound quality from their expensive components. Nelson Pass, designer/builder of my Threshold S300 power-amp recommends leaving it on 24/7 to avoid thermal shock each time. He also has the same view of his Pass Labs equipment. SS Pre-amps in particular, can take several DAYS to fully warm up, to the point where they're giving their full SQ potential. One of my previous Pre-Amps; a Jeff Rowland Consonance; the manual 'instructs' to leave on always as it can take several days (it suggests 6 days!) to warm up. Likewise DACs (not tubed), can take several days to fully warm up, and also many streamers too. So, leave such items switched on, always, unless you're going to be away from home for extended periods. (there's no risk to the Planet btw!)

I would not leave any tubed or Class A equipment on when not in use, as they; 1) run hot, 2) use lots of electricity, and 3) reduce their lifespan per hour. Electrolytic Capacitors eg have a surprisingly limited lifespan - some just a couple of thousand hours if run at rated temperature. With every 10°c reduction, in use, from rated temperature, the lifespan increases by 3x, which is why Class A amps usually use main Caps rated at 105°c, and they are expensive.

To @daveteauk ’s point, electrolytic capacitors are negatively impacted by inrush current that occurs every time power is turned on.

Since audiophiles are inexplicably obsessed with electrolytic capacitors and the urgent need to replace them all the time, leaving our gear on seems to make sense in that respect too.

Just watch for bias drift from time to time. 

@au_lait - No rocker or plunger switch on the back of the external DC supply?  There weren't many of those made...only a scant few Master Supply w no switches.