Warm-up time for amps and preamps

I have a class D amp.  The NuForce technician told me something very interesting: He said it's not good for a switching amp to be on without being connected to a running pre-amp with a source playing.  Therefore, when warming it up I have the tuner playing at very low volume.
i have a tube pre-amp (Conrad-Johnson) which also benefits from the warm-up.

It takes about an hour for my all SS system when "cold", meaning unplugged.  My gear has a standby setting which dramatically reduces the warm-up time, but there still is one.

I find that the phono section of my pre-amp is warmed up only by playing records
at fairly loud volume.  Just keeping the pre-amp on for a period of time doesn't do the trick.

 I know I contradicted myself in the last post.  When I got to think of it, the phono section of the pre-amp required separate warm-up.
Sorry!

auxinput is correct.
All solid state devices consist of metals, metal oxides and binders to bond them together. Overtime the solvent in the binders begin to evaporate and contributes to the resistor, diode or what have you, deteriorating.

I have mostly tube equipment, so I like to play a recording at low level, to put all electromechanical, and electrical functions of all components in a working state for 10-15 minutes or so (sometimes less), before I sit down to serious focused listing. I feel there is advantage to allowing the processed signal from you cartridge (or other source) to complete transmission thru your speakers, where the signal is processed thru the tube grids opposed to the tubes in an idle state, speaker motors in a working state warming up and working the surround material, interconnects  transferring signals, etc.