I came to say exactly this. 50 hours is completely crazy, and if you're doing it often, you should look for another place ASAP. Fuck, 40 hours is already on the verge of being crazy if your job is intellectually demanding.
I've worked in one startup, another one on the process of becoming a small corp (i.e., already adopting process in a much serious scale) and a corp. The best by far, if you value your life outside the job, is the corp. The worst was IMHO the second one, which had the worst of the two worlds: from the startup world, disapproval stares whenever you left without doing enough overtime, crazy schedules overall (I learned later that some mandatory things were actually illegal in my country) and permanent fire-extinguish mode; from the corp world, bureaucracy and lots of meetings. This was in Europe, not in the US.
I've worked in one startup, another one on the process of becoming a small corp (i.e., already adopting process in a much serious scale) and a corp. The best by far, if you value your life outside the job, is the corp. The worst was IMHO the second one, which had the worst of the two worlds: from the startup world, disapproval stares whenever you left without doing enough overtime, crazy schedules overall (I learned later that some mandatory things were actually illegal in my country) and permanent fire-extinguish mode; from the corp world, bureaucracy and lots of meetings. This was in Europe, not in the US.