Listening after your entire system was powered off cold for a week+

Yes, definitely. At first listen it sounds pretty good, but then it becomes clear that the sound is a bit 'hard' all around. Things seem to smooth out after a few hours as you have noted.

NO not this week.

To clarify it more, last week with hot weather and unpredictable (brownout) power in our area, I intentionally unplugged my RG power conditioner and everything in the system fully unplugged. Not something I normally do, usually listening every 3 days or so.

Normally I can power up the system and in 60 minutes everything sounds fine. For whatever reason this week it took 4-5 hours (this time around) after being unplugged 7 days. Would plugged-in vs. not plugged and turned off matter.

Its an all-tube system, tube DAC, tube preamp, mono tube amps and not sure that matters. At 1hr vs. 4-5 hours this time around, sounded quite different.

My local (50+ year in vintage electronics tech) who does a lot of mod work once claimed it has more to do with my unit’s "transformation saturation - and once all transformers in each of these four units are nice and toasty is when the magic happens", according his school of thought. A capable person who builds some really nice sounding pieces, custom built and modified AudioNote amps for ref. Someone who is super particular about all of the transformers used in all his gear.

I had a particular dual mono solid state amp with dual Torroidal transformers like this, always took (at least) 4hrs of warm-up and play time for it to hit its optimum operating condition and THEN it would sound right. Sligther better with 24hr warmup. Similar to what some Pass Labs owners report, taking at least 24hrs of on-time for things to sound right. My current mono tube amps (huge transformers) takes 4-5hrs to achieve its final set point. Perhaps this is old regurgitated talk for daily listeners who leave gear on all of the time. Happy Listening in any case. 😉

I don't have to disconnect anything for any amount of time to notice a difference upon start up. Whether it's the analog end, CD player or streamer, they always sound better after a half hour to an hour warm up. And keep getting better after that. Unfortunately that's the reality in my system. And no, it's not my ears getting used to it. Such is life when your system gets to a certain level. On a radio shack system it would sound the same cold or hot. Or at least you would not notice the difference. 

I leave my solid-state preamp on all the time.  The solid-state AB-class amps need 15 min. to sound right, and perhaps improve with more time on.   I would expect the system would need some time to warm up if the preamp were turned off, even if just a day or two.