How many times can a mystic use psionic body?

Question

If a level 20 Mystic character dies, his psionic ability has a chance to bring him back to life 1d3 days later on the same plane of existence. How often can a Mystic do this? Is it every time they die until they fail a DC 10 roll? Or is there some other limit to it?

If you die, roll a d20. On a 10 or higher, you discorporate with 0 hit points, instead of dying, and you fall unconscious. You and your gear disappear. You appear at a spot of your choice 1d3 days later on the plane of existence where you died, having gained the benefits on one long rest.

Answer 1

They can use it every time they die

You have quoted the relevant section and the only place where the ability is described.

At the beginning of Psionic Body it says:

You gain the following benefits: [...]

There are no conditions on the benefit so you gain the benefit unconditionally. Psionic Body has no limit or any other restriction on how many times they can be used if it did, it would say so.

Thus, every time a character "dies" they roll a d20 to see if they actually do.

Answer 2

There is no limit to it; why would there be any limit to it? Things do what they say they do, and nothing in the psionic body description indicates that it has any kind of cooldown—aside from the simple fact that if you don’t exist, you can’t die again, so it can’t be used again until you return and then would die again.

Even dying, for real by rolling less than 10, doesn’t really stop the ability from working—if resurrected, you would still have this ability and so be able to continue using it.

And again, the question remains: why should this be limited? A 20th-level adventurer of any stripe has a variety of methods of overcoming death. Resurrection has been available to clerics of that level for seven levels—and raise dead, which is nearly as good, for literally more than half their career. Sure, raise dead or resurrection has some drawbacks (the caster cannot cast anything else that day, the subject takes a penalty that takes a few days to wear off), but psionic body has a drawback too—you can’t do anything for 1d3 days. That’s better than raise dead or resurrection, but class features are supposed to make you more powerful—particularly 20th-level ones!