It's a shame RocketLab have adopted such a SpaceX-esque policy of employment. Surely it must be possible to build a rocketry company where employees work only 40 hour weeks...
Of course if you have kids, it's way harder. But I can get close to 60 hours a week by working 50 hours Monday though Friday, and then half days Saturday/Sunday. Still time for workouts, games, hikes, fun. The reality is school events/conferences will interfere, so 50-55 is probably more reasonable long term.
It's all in what you want to accomplish in life. To me my work is my hobby so I don't need time for others.
Of course, it all depends on how passionate you are about space. If I lived in NZ and had the expertise for it (my really serious embedded stints ended in college), I'd be there in a flash.
How about being more passionate about spending time with my own kids, and being able to teach them about all the cool stuff like science, space, robotics etc.. What is it with companies that want claim to build cool stuff to better the humanity, but forget that the people are what's really important?
To do hard things is hard. I won't say this specific job requires 12-hour days - that's probably because this is such a capital-intensive endeavor. There aren't many hard deadlines when launching to LEO.