you're talkin like some magic thing that makes people live forever
any scientific advance in the direction of immortality probably wouldnt withstand whatever destroys the universe, so i think it very unlikely that anyone would find themselves in the position of floating through space for a billion years as a single atom
to answer your question, i wouldn't take a pill that would make me live forever unless every possible scenario had been analyzed- for example, after 100 years, would your body begin to fail, and make life living hell? or what would happen if you got seriously injured, imagine living through a million years as a decapitated body... and after a million years, something will probably come up that was impossible to predict
i wouldnt mind a pill that gave me "immortality" for 100 years, and then just continuing to take them every 100 years until , and if, i wanted to die
probably never gonna happen anyways, but you made e think about it