I might not be sane (how would I know fully?), but there are several times in my life when I beyond-willingly worked 75-90 hours per week for months on end. I did it to ship a game, and two other internal products at other companies. Those periods look a lot like working, sleeping, eating, and walking among the areas where those activities happen. I loved my life in those periods and had plenty of freedom to choose to do or not do it, probably more than I do now with obligations to provide for my family.