I charge 1% equity in your company alongside your time, and nothing else. The next time I bring something unique I come to you first, and that is how the second percent is earned, and the one after it. If the idea does not work I take no equity and none of your time.
That single fact changes what gets recommended, and it should. A firm billing by the day has an interest in the engagement lasting. A firm holding equity has an interest in the thing actually working.
If a project is ten, fifteen or thirty years ahead, that is a roadmap, and roadmaps move. Something generational is a different object entirely, and in a working life you meet very few of them. That is the filter, and it is deliberately hard to pass.