I don't have one answer for this, unfortunately. It depends on how I'm feeling in any particular playthrough.
Sometimes I'll play for the mechanical nature of things, just fighting through the combats and pushing myself to see how far I can go without resting.
Other times, especially when I find myself connecting with a character, I'll slow down and reread everything and sleep whenever I think a reasonable person would need sleep. Which is to say, I think the average person would need rest a lot. Imagine, for instance, if you got into a fight today. And then another fight. And then another fight. With people dying each time. I think you would probably feel worn out pretty fast.
