I don't know if anyone has noticed, or commented on, this yet. The negative trait "Sleepyhead" (Needs more sleep) doesn't seem to work properly in single player. My characters don't seem to get the "tired notification" quicker or require more sleep. When I do get the base "tired notification" I still have a maximum sleep time of 7 hours. The only change that I have noticed, but not confirmed with a non-Sleepyhead character, is that I can have my character go to sleep any time I want. (Which is great in single player for setting the clock to daylight hours to increase survival.) Great game though, can't wait for NPCs and automobiles (even if they're just lootable boxes in the road in the beginning).