Why can't bands keep their level

Because I have started this thread, I have to admit, that my question might have not been accurate enough. The question should have been, "Why does some progressive rock bands can't keep their level?"
So, yes, it's true - there are some who kept their level. To a certain extend. But did anyone with a big name made his best work in the later years? I don't think so.
And I believe we collected a lot of reasons why this is the case. I have found a few reasons in this discussion that makes most sense to me - so for me, my question is answered.

There were no signs of decline whatsoever in Art Zoyd's output until
Armageddon (Armageddon itself is a strange album that surely doesn't qualify
for the highest ratings but that's because of its concept and function, not
because of diminishing powers); I just ordered Phase V and have no reason to
expect anything else than something great. It's so sad that Hourbette dies
recently; I think he still had lots to offer.

I saw Holger Czukay live in 2009 at the age of 71 and he was still creative
and sharp as a musician; he played quite a bit of new material that was
great, but hardly anything of this was ever released (a small bit is on
"Eleven Years Innerspace", I think). Ageing comes in thrusts and I think he
had a tough job caring for his longtime ill wife then, and aged strongly
himself before his death in 2017, but as long as he could, he was going
strong.

I just listen to 2005 music of contemporary composer Alvin Curran, born 1938
(as Czukay) and he's absolutely on 100% there; I heard newer stuff and he
still is; he still does live things occasionally and doesn't come across as
getting old and tired at all. Stockhausen was pretty bonkers at the end but
his music was still innovative. It's totally possible.

Fred Frith and John Zorn are still doing well. Being more avantgarde and
oppositional seems to help.

I'm pretty sure that drugs and alcohol play a big role in some people's
(incl. many rock musicians) ageing before time. Sober does better in the long
run (despite probably missing out on something at 20ish).

Actually, with a lot of modern prog bands, they get better as they make more albums and refine their sound. IQ is probably the best example of this, though I love their 80's work too. I think Neal Morse, The Flower Kings and Steven Wilson have continued at a high quality level too.

Every album is just a moment in time. It's a combination of ideas, enthusiasm and and circumstance. To quote Heraclitus, you cannot step into the same river twice. 

Apart from commercialism taking over, people get bored of playing with each other, people wear their repertoires out, it all becomes a drag, there are internal arguments, "creative differences" and the need to pay the bills - it all becomes boring and samey but you all stay together to pay the bills. 

Bands have a half life and tend to play best when no one person is in total control and you have floating members. 

Dellinger wrote: Yeah, but Pink Floyd is a weird case, since (at least for me), just about all of their albums are at least good. And they have so many fans that some will easily like the sound of one era, while not really being able to get into the sound of another (some love them because of their pop sensibilities, some love them because of their experimentation, some love them because of their long musical instrumental passages). However, I dare you find someone who likes Heaven & Earth (or Tormato, Union, The Ladder) more than Close to the Edge, Fragile, or The Yes album (yeah yeah, I know, there's tastes for everyone and you might actually find someone out there who does like H&E better).

*Raises hand

I like Heaven & Earth more than the vast majority of the early output...

While creativity might be stronger in youth, I think there is another better reason for why the best albums *tend* to the earlier one: record company involvement. In the late 1970s in particular, record companies put the screws on existing bands - they wanted a radio hit. Note that Fripp ended Crimson just before this kind of thing hit in the mid 70s, and generally didn't like making Crimson albums when he felt pressured. 

Dopeydoc wrote: Some exceptions: The Enid, IQ, Ozric Tentacles...

 

The effectiveness of a solo depends so much on the context. A good solo doesn't just support the music, it is the music (of course it's a part of the music). How integral it is and how integrated it should be into the greater piece depends on context and an individual's assessment. Sometimes a solo adds another dimension to the music, and an interesting opportunity to explore themes and create contrasts. It can work well in juxtaposition, or can be used in a more cohesive, straight-forward musical manner. In metal and hard rock I do tend to find solos boring as they seem too often to be added in just to show-off their chops rather than as a more "artistic" means to convey a feeling or to add to the feel. With many heavy metal acts, it's like a formulaic patchwork, insert guitar solo here, insert drum solo here, and doesn't feel organic. It doesn't to my ears add to the piece, but others enjoy it, and sometimes they're just having fun with it.

I often love hearing solo compositions where the whole piece is one solo -- I love solo cello, piano and xylophone for instance -- but in the band context, rarely does a long solo section added into the piece work very well for me. I have heard some jazz band recordings with some good long solos and many classical works where I felt that the solos (say in concertos) positively added to the musical experience, and it wasn't being done just for the sake of having a solo.

Side-note: There are many examples of shorter solos in rock that I think are very good, though I prefer it when they are acoustic instruments on the whole (guitar, violin, woodwinds such as flute, oboe, vibraphone, piano etc.). Hearing a solo instrument rise out of the rest of the band or orchestration to stand alone can be sublime.

I do think that one could come up with very long solos that work beautifully into the composition. Is it necessary, maybe not, but then ultimately what is? If that's their creative vision and it's not just being used to show off (see how good we are), then great.

Sorry, no sleep, and I know this is really badly presented/ written/ thought-out and rambling post.