First off, I am not certain it is such a bleak personal experience to work for these companies, an engineer friend at Space X HQ is usually pulling around 40-50h work weeks, which seems sustainable if a little intense.
Some industries operate under almost continuous crunches, the video games sector is notorious for this, and it might be that this is the case here too, and that my friend is just lucky to be on a team that is spared being overworked. It doesn't matter that people work on something they're passionate about, at a certain point it gets too much for anyone. I also got close to a burnout, and I did learn important lessons about managing my work life balance, working passionately while avoiding toxic stress, etc [wrote too much personal stuff, pasted under].
To get back to the point though, I wonder whether I would be able to remember these lessons and manage my work-life balance correctly, if I thought my work was as world changing as what Tesla and Space X are doing. I am deeply grateful that people like Elon Musk and the many others in these companies are willing to make decisions that might deprive them of time with their loved ones, potentially affect their health too, to bring such a change about.
I mean, the overarching goal of Space X to make life multi-planetary might seem like PR fluff to some, but I agree that we will extinguish ourselves if we stay on one planet. I would prefer that governments pool resources and achieve this public good through public means, as I find dangerous that a private company might end up having a monopoly on affordable space access. However, our governments fail on this and can't even agree on curbing climate change effectively, though it is a much more obvious danger, so I can only support Space X in their endeavor, and wholeheartedly wish them success.
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[the personal stuff] I once worked 6 months without a single day off (work weeks of about 90 hours), which to some may appear like a manageable amount of stress, but I was in my early 20s and didn't know how to do this properly. We did make our deadline and things that needed to happen in that time frame did, but after it, lo and behold, the cough I'd had for a month for no apparent reason suddenly stopped. Good that it did too, as my throat was so irritated I was coughing a bit of blood in the end. Sorry for the gory detail there, but just to point out that being overworked does have some very real and physical repercussions, besides also leading to painful life choices. Not realizing my grandfather was in his final days when he was admitted to the hospital with a bad cough, and not getting there in time to say goodbye, is my personal low point in this regard, and something I have regretted ever since. I wish I hadn't needed to make such a terrible error in judgement to learn this lesson, but I did not make this mistake again, and prioritizing family and friends over work, however important whatever task or deadline might seem in the instant, is something I very much kept it mind since. It has made me much happier, and hasn't negatively impacted my work output in any way I can measure.