Personally, I need multiple hours. I'm not the type to open my eyes, jump out of bed, and hit the floor running. I'm more the type of "fuck, why am I awake?" but then at the end of the day if there's stuff to do, I can be up for a while. So I'm much better at night than in the morning. Even if I'm my keyboard at 10am, I'm still not up to speed. My best comes later in the day. I think part of that is I've worked for places for so long that I was in meetings all day, and never got to do my actual job until late in the day when everyone else was winding down.