amp sounds different after cranking

The resistance of copper increases with temperature, so when hot, the windings of the amp’s transformers and speakers will have a higher resistance and so be more lossy. That alters the amp’s characteristics somewhat.
And human hearing is not linear, exhibits short term level shift, and longer term degradation, from prolonged exposure to high sound pressure levels.

I think you might be oversimplifying it a bit. It depends upon the venue, the musical format, and the age of the patrons. If you are playing for 20 and 30 something aged people in a dance or rock venue volume is important to the dance floor activity. People dancing sells drinks. If the volume is not pumping to a certain degree fewer people dance and less drinks are sold. I know this from first hand experience having been both on the stage playing and in the FOH running the sound system for years. A very large night club I used to be the FOH sound engineer for had high-end west coast circuit bands come through weekly. They catered to a college-aged crowd who were out to party. I used to regularly get grief from the bar staff for the volume in the room. I had a dB meter sitting on the sound board next to me so I knew exactly what the sound pressure level in the room was at all times. If it wasn't a certain level nobody would dance. If it was loud and people were dancing, and I turned it down just 3 dB it would clear the dance floor almost immediately. When the band first starts you don't want to blow people against the back wall but as the night progressed and the energy increased the volume needs to as well. I told the staff that turning it down was going to inhibit their drink sales but they didn't believe me until I demonstrated it to them. I had the club manager stand next to me in the booth once when he came to complain about the volume the bar staff was griping about. I showed him the sound meter and told him to watch the dance floor. I brought it down just 3 dB, which wasn't very much, and not as much as they wanted, and the packed dance floor completely cleared before the song was over. I told him that I had been doing that job for a long time and I knew what I was doing. I didn't get as much grief from the bar staff after that.  I had seen that same thing happen many times before.

If the band is playing oldies for people 40 plus in a sports bar or neighborhood venue you can't hit them with that much volume. They are there to visit with their friends and maybe dance a little. It has to be at a level where people can converse. It's not a meat market like the dance clubs are and has to be treated as such. The only time I was ever able to get a band sounding really good in a small bar at a low volume was when the drummer was using electronic drums. He could turn them down and they still sounded great. The band will usually play to the volume of the drums. If they don't then you're working with idiots, egomaniacs or both.  The fidelity of the band isn't as important in those situations.

I like to play loud as much as anybody but, there's a time and place for it. You just have to understand when and where that is.....but yeah, many bands play too loud.

Large glass or hard surfaces and sound do not play well together. Since indoor racquetball courts are your point of reference I'm assuming you have been in them before. It is a very reflective and reverberant atmosphere. It would sound terrible even if only one of the walls was all glass. From what I have seen, if the patrons want to converse, and the band is too loud, they just leave and go somewhere else.

I suppose it comes down to you are either a person who enjoys live music or you're not. There has to be a certain expectation from the patron's point of view, that if there is a live band playing, there is going to be a certain amount of volume to deal with unless it is all acoustic instruments. If they don't want to deal with that then they shouldn't have been there in the first place. Successful local bands know how much volume they can get away with. If they didn't they wouldn't have people coming to see them over and over again.

From a technical standpoint, it's not easy to be an electrified band in a small room. Especially if there are drums involved. In a larger room there is space and distance that will disperse the sound the farther away from the source you get. It's tough to pack a lot of sound into a small space. I'm not necessarily talking about sound pressure level (volume). Low frequencies do not do well in small rooms. Standing waves tend to build up in some areas and in others may be gone completely. Depending upon where you are sitting the perceived volume can be drastically different. If the band happens to be set up in one of the null zones in the room their first inclination is to play louder. Especially bass and drums. That can make it uncomfortable for people sitting in other places in the room. Many live venues have the stages for the bands in a corner. That's the worst place in the room for it from an acoustics perspective.

Some amps, especially ones with tube rectifiers, will get a little extra sag (spongy) at prolonged high volume. This is perfectly normal. Abnormally hot to the touch is not. Might need to bias those tubes a little cooler.

Point of interest: I *think* it was Eddie Van Halen that said your amp will sound its best just before it blows up. Then again, most of us mere mortals probably can’t afford to have countless amps around.

Ha. Got me there ninworks ! Yeah, I shouldn't have used a racquet court as an example...reflective floors ceiling, walls, etc.

I was thinking of some commercial buildings I've been in where the glass completely blocked the sound to a dead silence. Putting some kind of rug on a dance
floor wouldn't work either. There must be a workable solution in the world somewhere, even if everyone just wears earphones and dances !

And yeah, there's always a SMALL percentage of the human race that doesn't mind excessive noise in a small room. From a business standpoint, a bigger market(comfortable sound) is better than a smaller market(crazy loud sound). I think those who cater to the smaller market are paying the price !

And yes, the nuances of reflecting and absorbing freqs is always a challenge.

But dang it, I want to listen to live music without hurting my ears...and I'm quite willing to suffer the disgrace of having the band use half size drums or electric drums to do it !

Or, as sort of a compromise, only issue a license to play music LOUD to people that just have to play loud. LOL.

Or force bands to be rated for sound...eg : drunk/druggy band <50db sloppy garage band <60db somewhat tight intermediate band <70db semi-pro band <80db.

Oh well. I can only dream ! It seems most have their head in computer games or social media anyway.

But I think it's partly us musician's fault for being so dang loud !

But is it a bit addictive to hear a loud guitar tone through a hot tube amp cut right into your soul ?

Yeah, been there, done that.

Doesn't have to be that LOUD though !

I think a rethinking of the size and power of our equipment in the future may fix this issue.

We can all probably hear and experience good tone through the relatively small "sound volume" of our radios and stereos for instance.

Even old Stevie in full glory !

Right ?

And I bet it doesn't take 130db to do it...or 100db...or 80db either.

I think there’s a visceral dimension to loud music that just doesn’t scale down; at say 80dB SPL the dynamics are missing and it’s hard to generate musical excitement, perhaps due to that.