everyone talks about Grace's ailments post-story/epilogue and dying before Rocky due to lifespan difference but I think it's time we acknowledge ROCKY isn't in the greatest shape either. Dude was in an environment burning him for at least a few minutes, we know it wrecked his carapace and can assume it damaged his lungs. Then the radiation exposure, you know, the thing that killed his entire crew. We know that he was safer because of largely being around astrophage, but we also know he wasn't in his workshop/the engines the whole time. Eridians watch each other sleep, he would've been around the others a lot while they were still alive, and then after their deaths it's easy to imagine he'd be around the ship doing more things. And THEN on the way back to Erid when the taumoeba escape we know that the engines cut out but the astrophage are also powering the life support systems as Grace mentions. And this is all even without considering what funky gravity and mission food would do to a traveler