It's not just a Mugging. It's also a model that takes no account of agents trying to alter the chances of Hells. Sure, if Hell has a finite probability at any given time, then eventually it should happen, except that an agent is deliberately exerting continual optimization pressure to push that probability down over time.
P(Hell) exists, but its derivative over time is negative.
http://www.theatlantic.com/technology/archive/2015/05/immortal-but-damned-to-hell-on-earth/394160/
With such long periods of time in play (if we succeed), the improbable hellish scenarios which might befall us become increasingly probable.
With the probability of death never quite reaching 0, despite advanced science, death might yet be inevitable.
But the same applies also to a hellish life in the meanwhile. And the longer the life, the more likely the survivors will envy the dead. Is there any safety in this universe? What's the best we can do?