From my experience, it doesn't matter how long you let the tubes warm up. The amp won't sound its best until after 15 minutes of signal has passed through it. Ten minutes of idle is all it takes for a KT150 (the highest power dissipating tube out there) to reach operating temps, so I assume all other tubes require less. You're just killing tubes by letting them idle for hours before playing.
How long does it take your tube amp to warm up?
My tube amplifier has about 12 tubes and takes a couple hours for it to open up and sound really good and comfortable to listen to. Always wondered why it takes so long for a tube amplifier to warm up and what’s happening during this phase.
If I left it on for six or seven hours would it sound even better? I normally don’t leave it on for more than four or five hours.
How long does it take your amplifiers to warm up?