Can you leave class D amps on and not ever turn them off?

**Usually** keeping filter caps charged is a good thing for their lifespan. If however that means that the caps also are running warm then its not going to help, especially if some of that warmth comes from ripple current (which tends to be higher at higher frequencies as seen in SMPSs). Careful circuit design can avoid these problems.

As one who has spent a lot of time studying the idea of going off grid and using solar power and the like, one thing that comes up in sorting out how much power you're going to need is how long something is on, and not so much how much power it draws. Class D amps are typically around 85% efficient so a 500 watt amp is going to draw some power even if its just sitting there at idle. Since there is never dead silence even when the preamp is off, that means the output section is engaged even if its not making a lot of power reproducing background noise.

I get that some solid state circuits sound better after they are on for about a day or so. IMO this really says that maybe they aren't all that green compared to tubes if you tend to leave them on all the time so they will sound right.

Interesting thread. I'm using the trigger cables on my Wired 4 Sound mAMPs to power them on/off before/after each listening session. May try leaving them on for 24-hours to see how things go, but that sound pretty great with little to no warm-up time.

I'm running a Rogue Audio Pharaoh integrated. It's a hybrid- tube preamplifier and Class D power amplification. It also has two power switches. The front switch controls the preamplifier. The rear switch (meant to be left on at all times unless changing tubes or configuring the phono section) controls the Class D boards.

Transistors live longer when they're always ON.
They have life of up to 60k hours when ON and much shorter than OFF.
Electrolytic caps also benefit from being always ON except if under high temperatures. Leaving on even clas A/B amp isn't a problem if one does not dissipate excessive heat. The only now consideration is power line and if there's ever been an issue with lightning strikes. Than you will have to power down when leave home or at least when disaster is expected. There will be no surge protection of components if hit by lightning.
Class A solid state amps and tube amps always should be turned off when not attended.