I find it hard to believe that the most successful startups are the ones who code 80h per week unless you guarantee that the output of the code is big $$$
You have to convince your stakeholders that further investment is worth it. But I also think that the "go big or go home" strategy comes from seriously messed-up incentives. It might be justified if the margin is very low or if aquiring a big user base for other purposes is the actual goal.