How long it take before your system/amps sound

I leave all my usual stuff on 24/7/365 because it sounds better after 24 hours being on.
I have almost all solid state. Only a Tube preamp i use as a glorified tube buffer for my digital stuff has four tubes. I still leave that on 24/7 anyway.

Yes..
stuff gets better after a few hours.. some better still after 12 hours, and some the final really best is over 24 hours..

I have an Audio Research Sp-15 I keep around to use the tube phono section. I only turn tht on before I use it. That takes at least three hours before it sounds reasonable.

I let my car idle all the time because it just runs better and hey, I can afford the gas.

I have mostly Solid State and leave it on 24/7/365 as well. My Unison Research Unico SE hybrid tube integrated gets better with each hour it is on if I shut it down due to travel or inclement weather.

My power company recommends that all audio and video be left on 24/7/365. I was surprised they were so knowledgeable about high-end audio.

For me between 6 min and 1 hr. I have a tube integrated and it takes about 6 min for the tubes to get the bias up. After an hour they are fully warmed up. The difference between the 6 min mark and 1 hr is hardly noticeable.