I use lava rock in terra cotta pots. It allows and requires daily watering. Mounting also means daily watering. Not all orchids do well mounted. But many will mount.

It depends to a large extent on where you are in the world.

Growing mixtures and methods vary widely depending on climate. "the longest lasting material" might mean extra watering and fiddling with your growing environment where you live.

LECA and semi-hydro pots?

So far, red lava rocks of diferent sizes is best substrat.

I grow many phals in LECA which is inorganic and does not degrade over time. It is open and airy like bark. It is also possible to use this media in semi-hydroponics so it is quite versatile. The only negative of LECA is that it can accumulate salts and fertiliser over time but pots can be flushed with water. It dries slightly faster than bark but in my environment this is hugely beneficial (I'm from the UK - quite cool and wet). When the pot has no more condensation in it is about right for watering. There is also treated bark such as Kiwi bark and Orchiata that claim to last longer than normal bark so this can extend the period of time between repotting but it will eventually degrade.