My response last night didn't post, so I'll try again:
I agree with Ralph et al that cool-running Class D amps don't require long warmup before playing perfectly. That said, my earlier career in lab equipment design and manufacture suggests that the key to optimal performance is apt to occur when isothermality is reached. With my old Pass Labs Class A amps that warmup effect indeed took 1-1.5hrs. This was a great annoyance, as keeping them running 24/7 at 600w idle heat was VERY annoying to both my pocketbook AND Mother Nature.
My ArgentPur GaN-FET Monos reach isothermality (100F) in less than 30minutes. More importanntly, at 11w idle it's convenient to power them 24/7.
Yet I want to address another factor that I believe is at play, especially with those who remarked that their systems don't sound great until a brief warmup of, let's say, 10-30min. My contention that this is a human ear-brain acclimation period to a novel acoustic environment, perhaps remarkably different from the prior acoustics, let's say, of your kitchen, bedroom, outdoors, in your car, etc. We simply need time to acclimate to the listening room, especially if there's a dedicated listening chair and well-sorted soundstage. I believe that this ONE of that program directors and conductors play a throw-away introductory piece before the main program in a serious concert. Of course other reasons, such as late-coming audience noise, musician warmup and large force temporal gelling are in play. It may be that the first few minutes don't sound necessarily BAD, but it does SOUND different a few minutes later...and usually for the better. Thoughts?