You can't. After a few solid months of 70 hour weeks you start seeing some serious health effects (blood pressure spikes, nervous system issues triggered by high levels of persistent stress, insomnia, exhaustion, etc).
This is quite a generalization. It depends on how much you value and enjoy your work. And, every person's limit is different. There exist people on both extremes.
70+ hours of sustained work per week is unsustainable, the human body largely can't handle it. SV has a lot of dumb mythology around working non-stop (i.e. Musk claiming he works 100+ hours a week), but what people usually call 70 hours is 50 hours of work and 20 hours of dicking around 'working'.
It's a generalization that the data seems to support.
Sure, there are always outliers, but in general, 70+ hours per week over several weeks to months will severely damage your health.
Note that we're talking about 70 hours of actual work. Being in the office for 70 hours but only working 50 hours is what's more common, and doesn't cause the same hit to your health.
