In today's world, the end of the world is not the scariest thing for immortals. Even if you can't die, you can be (and will be) captured by the ultrarich, tortured and experimented on to get the benefits of your condition without the downsides. Before or after that, whichever comes first, you'll struggle to have enough money for constant relocations and for buying fake identities.
I gotta agree with the poster above. I've watched the anime multiple times, and if the manga is going to follow the exact same plot, well... Nonetheless, I'm sure diehard Nanoha fans will love this :P
I'm that diehard Nanoha fan XD I rewatch the anime and reread the manga from time to time, and every format has some cool unique thing in them that makes me love them. I am looking forward to what is going to make this adaption special :)