Better sounding after 1 hour

It's common in all higher end gear, and some can take quite a bit longer. Had a McIntosh C2300 tube preamp that took over 3 hours to really sound right. Some folks will leave their stuff on 24/7. Transistors are usually a bit faster to warm up, but not always. I've heard stories about early Krell amps that needed 4 or 5 hours of warm-up.

I'll agree with the warm up period. I've taken to turning my equipment on when I get home for when I listen to music later in the evening.

My ATC integrated is SS and like the other posters, I think it sounds better after about an hour. I read it explained somewhere that this is because the final factory biasing is done after bench output testing, when the amp is hot. Don't know if it's true, but it was one of the more plausible explanations for the effect that I've read.

All electronic component parts operate best (at their desired specs) when they have reached thermal equilibrum. I will let my system play for 30 min or more before begining a session.

Yes. With tubes is it always the case. It depends how long it takes, if the tube amplifier has an automatic bias it is much shorter.