Do amps sound better when left on for 30 minutes ?

Do amps sound better just by having it left on for a while, or do they have to make sound in the warming up process ?

Mine does, not sure about the cheese types though.
How would anyone know the answer to this critical question? I guess they would have to listen and decide. I'll do that for you for $100 or you could just do it yourself for free. Let me know what you decide is the best course.
Most every piece of equipment benefits from some warm up time. Generally, turning them on is OK, but it might take a little longer to warm up than if it was pumping some music through it, even if that music is playing at low volume.
My experience is that they don't warm fully unless they are playing music. I can leave my kW500 on for hours and it still needs playing time before it performs at its best.
I agree with the idea that playing the equipment speeds up the warming period. Also solid state takes along time to get stable on cold startup. That's why I usually leave my solid state on 25/7. I turn my tube equipment off, but they too warm up much faster when played rather than sitting silent. Tubes also get to a stable point faster IMHO.
It's actually pretty much an industry standard to leave solid state equipment on all the time. The designers say that the "rush" from turning on and off is more detrimental to the equipment. Tube gear, of course, would burn through tubes too often, so they need the half hour or so of warm up time.
I have a tubed amp and preamp and they always sound better after a warmup time of 30-60 minutes.
I have tube equipment and turn them on and put cd on ( low volume ) play for 45-60 minutes..Usually cd is finished and is ready to go.......
I warm up tubes in amps 30-45 min as to not stress the tubes and shorten their life span. It seem after an hour to an hour and a half of playing everything starts to settle in and the system sounds more liquid (homogenous).
I concur with Thorman . Works for me !

Happy tunes.
Product literature from Audio Research supports the idea of 'adequate warm up time' before critical listening occurs.
Thank you for all the replys !
I will leave my SS amps on all the time now...

Where did you find the extra hour each day?
If you're willing to part with it, I'll pay big $$$!
My Man.....It must have been leap day
even my non-audiophile friend could hear when my tube amp was warmed up, about 30 minutes.
I think it depends on the amplifier. I have owned both tube and SS amplifiers mfrd by Quicksilver, McIntosh, Threshold, and Ayre and I can tell you from my experience I have never noticed a difference.