For many years my big system needed about 20-30 minutes of playing time to sound its best even with everything powered on 24/7. I believe it was the tubes in my preamp and dac but the Sumo Nine Class A & Audio Alchemy transport warm up as well. The transformation was fairly subtle, mostly image but I'm sensitive to that. It went from closed in sounding to a very open and deep soundstage.
Now that I am computer based playback, solid state dac, and a Levinson power amp it sounds the same turned on fresh as it does hours later so it really depends on the gear itself
Now that I am computer based playback, solid state dac, and a Levinson power amp it sounds the same turned on fresh as it does hours later so it really depends on the gear itself