Would increasing the percentage of lava in substrate make it last longer between repots.
Thinking being that lava disintegrates far slower than akadama.
I generally use a bonsai nursery ...mix.
Which is lava, akadama and pumice. (hopefully.... )
The mix seems stable for quite a long time (usually over a year or so) but would increasing lava ....ADD.... to that duration?

Yes, akadama disintergrates in less than a year in my conditions, but iceland lava I use seems to last forever. I sift it out when repotting and reuse it. I never repot due to dissintegrated soil. I repot due to rootbound trees.

Oh me too. I'm just asking to determine if I can increase time between repots by adding lava.

I do not think more lava rock will make the roots grow slower. If that is the case, the time between newly repotted and root bound will not change.

Well maybe an overambitious root may run into a lump of lava and decide to wait a bit before getting bigger. lol

Even if I understand it was ment as a joke, In some way you made me think. Akadama breaks down and when doing that leave more space for roots to grow. Not that I think it makes a big difference. But if any difference more lava would leave less space for root growth and thereby shorten the repotting interval. But I really think the difference is negligble.