To take it a step further, ceasing to exist is a scientific impossibility because time is relative to space. this means a couple of things:
1. Time can be almost infinitely stretched, such as at or around a singularity within a black hole.
2. Anything outside of this universe is not bound to this universe's time (because it's relative to our universe's space). So like a book, it is more than likely that someone standing outside of the boundary of our universe (which is possible because our universe is expanding into something) is in an existence where our time is not singularly linear (going only in one direction). Ultimately that means once you exist, you will always exist and have always existed (in our universe). Like a character in a book. he is bound by the book's time scale, but the reader isn't. We can jump around from beginning to end, but once that character is introduced anywhere in the book, he is a part of the book whether his part is small or large, and he can never be seperated from it.
The bottom line is this. Ceasing to exist completely is not a likely outcome scientifically.