Better sounding after 1 hour

I would agree with Elizabeth but also slightly disagree I think this effect is more noticeable with tubes after about 30-60 mins. At least it has been and continues to be with my gear and gear I have owned previously.

I wouldn't leave tube gears on 24/7. This will shorten their life. Solid state, especially preamp, can be left on 24/7. Yes, most audio equipment sounds better after some warm up.

Tube electronics changes more quickly than solid state making tube warm up more obvious. I have owned tube electronics that warmed up in an hour and solid state electronics that has taken as long as 3 days.

Years ago when I got my Rogue Cronus Magnum, I couldn't wait more than 15 minutes for it to warm up the first time i used it. We started spinning tunes and it was mediocre at best. About 10 minutes later it opened up to the point I was practically in tears. I can't imagine what it's like for these people with much higher end gear. Yes, tubes do that.

Tube gear usually takes about an hour or so to warm up and sound it's best. Soild State can take 4-12 hours to warm up to sounding it's best, which is why many who own SS gear leave it powered up 24/7.