Couldn't agree more. Intense can be due to working on really hard problems (or even the extra time/energy to learn something new). Just as easily, it can be due to poor planning or improper communication within the company. Unfortunately, if one is passionate about doing a good job and enjoying what you are doing, you might not be able to realize when your extra efforts are really the expectation than what should be the norm.

The fact that the OP was able to grasp this particular issue so early on shows a maturity and insight that even senior engineers who go to work at startups might miss.

I know I've had my moments.