I turn my Hypex powered Marantz integrated off overnight during unsettled weather. About 20 minutes after turn-on, it’s back to peak.
When I had an all-tube Cary SLI-80, it would take 45 minutes to an hour to sound its best.
Then there was the class A Pass Aleph. If it was shut off for more than a couple of hours, it wouldn’t sound its best til the next day!

