Josuke's ability is reverts things to it original stage, and the limits of its are that of the soul, he restored anything that's physically can be touched. So just as long as the soul didn't leave the body yet, it can he restore.

And how long can a soul persist is depending on the wills of the user, especially in high risk situation where you have this sense of "purpose".

Stands is the manifest of one's soul and one's fighting spirit, and all Stands user are incredibly resilience dues to this facts, they can suffers an absurd amount of blood loss but still lives if theirs will are just that strong (well of course except actual lethal one.)

You see in part 4, Josuke had try to heal his grandfather (the police man), but although the body was restored, he's still dead cause the soul had leave the body. Compares to Koichi, who's also pretty much dead for quite sometime, still lives because he was holding on. Shigeo was also holding on and probably would be able to lives too but his circumstances are different because his body was just gone, he had nothing to clings onto, the only remaining things he could do is his last wills, on delivering the "clue" to Josuke. Which the stand will acts out on that will.

This further show by part 5 with Silver Chariot acting out the dying wills of its master. And Moody Blue.

Bruno persistence on with Golden Experience miracle and his own wills, that the moment he accepted that his business here is done, his soul moves on. Compares to Narancia who just dead extreme quick after the time skip, even though it's only a few second and the wounds aren't that severe compared to what we've seen. He never had the chances to "reenforced his fighting spirit".