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

Anyone who said warm tubes would sound better is correct. They sound much better than cold tubes. I was thinking of the leaving them on all the time part of the question,

Even with solid state gear, there is some debate about the disadvantages, in terms of equipment longevity/reliability about leaving gear on 24/7. First, there is a possibility, however remote, of failure that could cause a fire. Second, there is the issue of lightning strike or other powerline calamity (some people unplug gear completely when not in use to prevent that kind of damage). The third concern has to do with heat--high heat will shorten the life of any component. If you look at specifications for parts, such as resistors, transistors and capacitors, the lifetime projections show shortened life expectancy for higher heat conditions. Some people will say that certain parts, such as electrolytic capacitors are actually better off being charged all the time, but, the flip side of that is the heat issue. One should check with the manufacturer about this sort of thing if ultimate longevity is a big concern; in terms of sound, fully warmed up gear, whether tube or solid state, sounds better.

I very carefully experimented with a Unico hybrid. It would take two days to sound its best, with significant changes at 2/4/6/8 hour marks. Even swapping hot tubes with cold, the amp otherwise fully warmed up (i.e. on for at least two days), took four hours for the sound to stabilize (and improve). I tested over several weeks, rolling my fair collection of 12AU7's. Speakers were Fostex F120A single driver augmented with electrostatic super-tweeter.
-- William

Everything warms up Dude!!

Larryi, Electrolytic caps are worse with temperature. ESR increases with temperature sometimes even causing thermal runaway when capacitor heats itself by ripple current times ESR (mostly old dried-up caps). On the other hand electrolyte eats dielectric - aluminum oxide over long time storage. Voltage rebuilds layer of aluminum oxide keeping breakdown voltage up. Temperature is causing also electrolyte to dry-up cutting life of capacitor by half for every 10degC increase.

Temperature also changes viscosity of ferrofluid used mostly in tweeters but sometimes even in midrange. My speakers (Hyperion HPS-938) have 6.5" midrange without suspension (spiderweb) using ferrofluid as a suspension.

Yes, parts (including semiconductors) are getting worse (fail) with temperature but it is very small effect until you cross about 100degC where numbers of failures starts getting very high.