general relativity - How long can a particle survive inside of the horizon of a black hole?

By examining the causal structure of a Schwarzschild black hole, one can see that a particle in region II is unable to escape to $r=\infty$.

Such diagrams do not show, however, how long a particle can survive inside of region II without hitting the singularity. Can a particle survive indefinitely inside of the black hole? If not, is there a maximum life span of a particle inside the horizon?