Warm-up time for amps and preamps


How long does it take for your system to sound good from a cold start?
I try to keep my system on most of the time.  But occasionally I turn it off and it sounds like crap for a good half-hour to an hour.
i know there has been discussion here on the virtue of leaving tube preamps on all the time.
But my solid state amp (modified NuForce mono blocks) technician advises turning even them off occasionally.
128x128rvpiano
In response to ghosthouse, the psycho-acoustic effect is enhanced even more with a glass of Scotch.

I’m running a Class D Taranis by Merrill Audio. Got a bit concerned by rvpiano’s tech’s comment about "on with no input signal" being bad for Class D. 

There is absolutely no reason why running without input signal would be bad for any class D amp.  This strange advice was given by NuForce technician?  Are they still in business?
Starting with the sources...

VPI recommends turning on the table 30 minutes before use (VPI Aries)
AT-OC9/II phono cartridge usually takes one record side / 20 minutes to sound "right"
Herron VTPH-2 comes up the same time as the OC9/II -- 20-30 minutes
Transport takes zero time
DAC takes about an hour though I often just leave it on
Herron VTSP-3A about half an hour
Herron M-1 amps varies so I leave them on 24/7
Speakers need time depending on how long they have been idle.  Anything more than two weeks takes as much as an hour, maybe more.

My typical listening session starts an hour or more before I actually start listening.  I power up the entire system and start playing music through the DAC.  If I'm going to listen to vinyl, I play one record side while I listen to a CD through the DAC.  I do not leave the turntable playing a record unattended.

The original NuForce is not in business, but there exists a technician who worked for them who is in business (called TDSS) repairing and upgrading NuForce equipment.