I think it follows from Brian's point that only founders may ever put in that much work, maybe very early employees; as he said, the trick is to be painting your own house... Having said that, I completely agree that long hours are overrated and maybe unhealthy. Burnout will follow. Everyone has to recover. Such long stints can only be kept up for so long!
Is that true? I avoided ever joining startups because I assumed everyone worked 60 hours every week.
As the other reply says, usually you find people doing longer hours in a few selected periods of a startups life. E.g. First MVP, first big client... crunch time!