Companies full of 80 hour/week people are waiting to implode.
I'd agree with you, but somehow Amazon continues to succeed while allegedly driving their devs (and the rest of their staff) into working ridiculously hard all the time.
I also witnessed a project recently that has been driving people nearly that hard for nearly 5 years. It's not going well, the (remaining) employees get by more on their bonds of shared suffering than 'passion', 'drive' or whatever euphemism companies are looking for these days, but it's still going!
I know I can't survive more than a couple weeks at 60+ hours, but somehow, it's done; I've seen it done and it seems to be working for well Amazon.