My Sim is on 24/7, as they recommend. Even then, I warm it up with music, fairly loud, for 15 minutes or more before settling in for serious listening. The difference is not subtle. Most improvement comes in image and soundstage depth and, well, warmth.
Plinius warm-up
I've read on these boards the issue that the Plinius 8200 needs plenty of warm up time to sound right. This has been my experience also. I was wondering if other people are hearing the same specific qualities that I am. When the amp is not warmed up, the mids and highs play back level is lower, the lack of frequency balance giving the amp a bland sound. But the bass seems to be just fine compared to a warmed up amp. Same for you?
Don
Don