Indeed. One of my favorite things about thru-hiking is that you get a ton of sleep: it's not unusual go to bed shortly after sunset and wake up at sunrise.
I usually feel like crap hiking if I'm not in bed for 10+ hours. Mostly that's not hard - you're tired, and just sleep all night. It was a pain in the ass in Alaska, though; I think I'd have real trouble with long hikes there in the summer.
I actually found kayaking and hiking in Alaska amazing (I was only there for 2 weeks). We'd be going for 12-16 hours a day but the constant sunlight made me feel super energized and happy.
