does your system "warm up" and then sound better?

The 'no for tubes' is not true for preamps.
I have left my VAC Standard on so far, with used tubes on 24/7 for two years now with no deterioration.
Many tube preamps can go for a very long time before replacing tubes..
Not so tuube amps.And you should never leave a tube amplifier unattended anyway..
(My tube preamp is sealed, so I am far less worried about a fire in it)
All mine has are (2) 12AU7 and (2) 12AX7

So do you recommend that leave my pre amp and cd player on too? Also, do speakers "warm up"? What about cables? If so, how long does it take? Thanks for the info everyone! :-)

I think Mechans meant its not a good idea to leave tube gear on 24/7. I have to agree. Tube gear, just like solid state, usually benefits from some warm up time before listening.

To the OP; leave everything on that you can. If you leave your CD player and preamp on all the time, you should notice a nice difference. I have a CD player that takes several days to sound right after its been powered off.

I leave my CDP on all the time. It draws little and never heats up. Same for my DVD player. My integrated gets too warm for my tastes if I leave it on for a day or so, so I only turn it on and try not to listen for about 30 minutes as I can really tell the difference as it warms up from a cold start.

A small sacrifice to pay to the audio gods and my patience.

All the best,
Nonoise

Yes. Speakers. They have bits that move. It's the moving bits that make noise by vibrating. We call this noise music. Vibrating bits vibrate differently at different temperatures. Different kinds of vibrating will make different kinds of noise. It's, like, science. You could call it, "warming up." It's not (just) in your head. Things just start to come together and cohere just so-ly after about an hour with every set of speakers I've ever met.

As for the electronic bits that just sit about and pass electrons, all passive and not moving like, folks'll tell you warming up matters. I leave mine on all the time 'cause it's easier than wondering why I've never heard any difference. But, been years since I've really turned any of it off, so what do I know.....