If I may jump in, please. I have three audio systems, and I keep them all going.
Primary: BCD-3, BP17c, Mag Dyna FM tuner, 4Bc, Thiel 2.7 speakers with ss2.2 sub
Secondary (building it for my son): Cambridge CD transport, BDA-2, BP-26, Mag Dyna FM tuner, 4Bsst2, AR3a speakers.
Bedroom: Cambridge integrated, Mag Dyna FM tuner, ADS monitor speakers.
I keep all of them running. Since the home is all electric, the monthly electric bill isn't appreciable.
Like Elizabeth, I believe having a truly warmed-up system is preferable to a turn-on and waiting for some time to achieve the best performance.
BTW: Back in my Ham Operator days, I kept both the transmitter power supply and the receiver on "standby" for days at a time so I could immediately answer the CQs.