Just because there is a possibility that my work could be made obsolete, I can't stop working. That is a non-starter. Why do you think people keep working on various fields like physics when most of them are theories that might be disproved very soon?
You are also forgetting the reason where you want to address the engineering need in you: Some of us have fun making this. Believe it or not, We want to do this :)
I do have other time that I spend with my family etc. More or less is personal preference. Family is one of those things that one can sink in infinite time and still feel incomplete - we all strike balances. FWIW - I sleep only 6 hours or so, so it provides a bit of a leg up. I usually nap a bit on the weekends though.
My meta-point is: Some people look at a job as a means to make a living. I look at mine as an opportunity. Here I have a company that is willing to put millions of dollars in the direction I point at or into the work that I am doing, based purely on trust. This kind of scale / experience is impossible to get by myself. For this I have to go the extra mile. The end result might benefit the company, but I find joy in the process of creation.
The company is not exactly chintzy either. They compensate me well enough to keep that from becoming an issue to me or my family.