This is very much a Philosophical question. Will there be an exxe thirty years from now, very possible, in thirty centuries, very likely much less so as with other relics from the past. Change is constant and all matter will eventually return to the cosmos including planet earth with each and every item and idea of human creation.
One of my hobbies is restoring scientific and electronic instrumentation including microscopes. The really nice and significant ones are built to last life times with proper care and proper use by individuals who understand them. Most are design to the very limits of what is possible given the laws of Physics and the technology available at the time of their design and construction. Did the individuals, companies and all involved need to do this, NO, but they made a intellectual choice to do the very best possible. The results were, as time past, others who appreciated their efforts continue to appreciate them and use them as they were intended. IMO, this is a responsible way to using Earth's limited resources and an expression of art & science blended into a tool that can be helpful in many ways.
The current crop of electronic instrumentation and similar is often not designed or built this way, they are designed and built to a price point intended to be obsolete and disposed of once a problem occurs as they are essentially non-repairable. Good for profitability, bad utilization of Earth's resources. Beyond this some of this stuff is truly awful to use.
Getting back to why using the very best materials possible for modifications and restoration of an exxe, consider one's time, resources and more that is consumed in any of these projects. IMO, one's time is FAR more valuable than the cost of materials involved as once the finite time available to an individual cannot be replaced. There is also the do it properly the first time to significantly reduce and prevent any possibility of doing that project again for an extended time. Again, this becomes a Philosophical question.
There is also the perceived monetary and market value of any exxe. In the case of a vehicle like a Lancia D24 which is very rare with significant market value, there is significant incentive to spend the resources required with very modest limits on cost to make it proper. Given the oppressed market value of the exxe, it is deemed unworthy of the best possible resources applied to make it the best it could be.
Know the market value of any vehicle is more often than not perceived by it's audience rather than the vehicles design excellence, craft of build or content.
As for the exxe chassis, occupant survivability in a crash is not quite the same as chassis designed for suspension geometry stability under load. Example, the NA Miata meets Fed mandated crash requirements yet it's chassis has the rigidity and stability of a boiled pasta noodle. If one is going to expend one's life time and resources to do a proper restoration, repair or improvement, why not do the very best possible.
Bernice
Another point I wanted to add is why all the concern about using SST for the coolant and heater tubes? The factory used non-SST and they last for 30 or more years and probably longer if the proper coolant mix was always used. Without sounding like the voice of doom (this happens as you stand on the doorstep of being 70) do you really think you will still have your X 30 years from now?
I'm not adverse to issues discussed here, just wondering.