There's always a lot of discussion on art forums about using quality materials, some say yes, it's needed for longevity, others say no, cheap gets the same results so why spend so much money. My feelings are that people have taken time over the centuries to share what they have learned the hard way. Certain colors have been proven to be fugitive. Some papers disintegrate. Some finishes crack.
If you want to be an artist, be a good artist. To be a good artist you have to learn your craft. We study technique so that we can learn the best way to communicate. We strive to develop our own style so that we can communicate our own unique way of seeing. Whatever message we send in a work should be a worthy one, hopefully just as relevant in a thousand years as it is now.
Now there's nothing wrong with communicating in a medium that is transient, as in ice or sand sculpting. There's a certain poignancy in saying beauty sometimes only lasts a moment, so enjoy it while it's here, but collectors aren't paying money for this art either. When a collector buys a piece of art they want to enjoy it for as long as they own it. Perhaps they want to pass it down so their ancestors can also enjoy it.
Proven quality materials are the way to ensure that your work will last. It's an honesty that you are giving the buyer. Some materials are new to this past century and maybe not proven by the test of time, but we do have chemistry to tell us the expected longevity.
The thing that struck me looking at the photo of the mural was the craftsmanship. I saw the attention to detail and marveled at the cryptic symbolism. I felt the artist and for a moment I stepped back into a different world. And it's all due to the fact they they obviously used the best materials available (this was a King's tomb after all) and took such pains to preserve it.