The Legion of Lazarus by Edmond Hamilton, Science Fiction, Adventure (Paperback) (ISBN-13: 9781463800222)

"It isn't so bad," says one of the men who are with you inside this ultimate room. "Fifty years from now, the rest of us will all be old, or dead."

And then you're waking again, and you think, Fifty years. you think. It's been fifty years.

But another part of your mind says, No, it is only tomorrow morning.

It isn't the dying itself. It's what comes before. The waiting, alone in a room without windows, trying to think. The opening of the door, the voices of the men who are going with you but not all the way, the walk down the corridor to the airlock room, the faces of the men, closed and impersonal. They do not enjoy this. Neither do they shrink from it. It's their job.